[sw, rom_ext_signer] Rearrange the `rom_ext_image_tools` directory

The top level directory is meant for N different ROM_EXT related
tools, hence signer has been moved into it's own sub-directory.

Signed-off-by: Silvestrs Timofejevs <silvestrst@lowrisc.org>
diff --git a/sw/host/rom_ext_image_tools/meson.build b/sw/host/rom_ext_image_tools/meson.build
index 282c4aa..b620c90 100644
--- a/sw/host/rom_ext_image_tools/meson.build
+++ b/sw/host/rom_ext_image_tools/meson.build
@@ -2,64 +2,4 @@
 # Licensed under the Apache License, Version 2.0, see LICENSE for details.
 # SPDX-License-Identifier: Apache-2.0
 
-cargo = find_program('cargo', required: false, disabler: true)
-
-build_type = 'release'
-build_dir = meson.current_build_dir()
-manifest_path = meson.current_source_dir() / 'Cargo.toml'
-toolchain_file = meson.current_source_dir() / 'rust-toolchain'
-
-# CARGO FLAGS:
-# These flags will only apply to the final binary, and won't get propogated
-# to the dependency crate builds.
-cargo_flags_array = [
-  'manifest-path=' + manifest_path,
-  'target-dir=' + build_dir,
-   build_type,
-]
-
-cargo_flags = ''
-foreach flag : cargo_flags_array
-  cargo_flags += '--' + flag + ' '
-endforeach
-
-# RUSTFLAGS:
-# These flags will apply to all the dependencies, as well as the final
-# binary. Linker and linker flavor amongst other things can be passed through
-# these flags.
-rust_flags = ''
-
-# The cargo invocation script.
-cargo_invoke_cmd = meson.source_root() / 'util/invoke_cargo.sh'
-
-rom_ext_signer_raw = custom_target(
-  'rom_ext_signer_raw',
-  command: [
-    cargo_invoke_cmd,
-    cargo,
-    cargo_flags,
-    rust_flags,
-    toolchain_file,
-    meson.source_root(),
-    meson.build_root(),
-  ],
-  depend_files: [
-    cargo_invoke_cmd,
-    manifest_path,
-    toolchain_file,
-  ],
-  output: '.',
-  console: true,
-  build_always_stale: true,
-  build_by_default: false,
-)
-
-rom_ext_signer_elf = custom_target(
-  'rom_ext_signer_elf',
-  command: ['cp', '@INPUT@' / build_type / 'rom_ext_signer', '@OUTPUT@'],
-  depends: rom_ext_signer_raw,
-  input: rom_ext_signer_raw,
-  output: 'rom_ext_signer.elf',
-  build_always_stale: true,
-  build_by_default: false,
-)
+subdir('signer')
diff --git a/sw/host/rom_ext_image_tools/Cargo.lock b/sw/host/rom_ext_image_tools/signer/Cargo.lock
similarity index 94%
rename from sw/host/rom_ext_image_tools/Cargo.lock
rename to sw/host/rom_ext_image_tools/signer/Cargo.lock
index 2296cd0..a0d76c8 100644
--- a/sw/host/rom_ext_image_tools/Cargo.lock
+++ b/sw/host/rom_ext_image_tools/signer/Cargo.lock
@@ -8,9 +8,9 @@
 
 [[package]]
 name = "cc"
-version = "1.0.61"
+version = "1.0.65"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ed67cbde08356238e75fc4656be4749481eeffb09e19f320a25237d5221c985d"
+checksum = "95752358c8f7552394baf48cd82695b345628ad3f170d607de3ca03b8dacca15"
 
 [[package]]
 name = "cfg-if"
@@ -50,9 +50,9 @@
 
 [[package]]
 name = "once_cell"
-version = "1.4.1"
+version = "1.5.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "260e51e7efe62b592207e9e13a68e43692a7a279171d6ba57abd208bf23645ad"
+checksum = "13bd41f508810a131401606d54ac32a467c97172d74ba7662562ebba5ad07fa0"
 
 [[package]]
 name = "proc-macro2"
@@ -102,9 +102,9 @@
 
 [[package]]
 name = "syn"
-version = "1.0.48"
+version = "1.0.50"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "cc371affeffc477f42a221a1e4297aedcea33d47d19b61455588bd9d8f6b19ac"
+checksum = "443b4178719c5a851e1bde36ce12da21d74a0e60b4d982ec3385a933c812f0f6"
 dependencies = [
  "proc-macro2",
  "quote",
diff --git a/sw/host/rom_ext_image_tools/Cargo.toml b/sw/host/rom_ext_image_tools/signer/Cargo.toml
similarity index 95%
rename from sw/host/rom_ext_image_tools/Cargo.toml
rename to sw/host/rom_ext_image_tools/signer/Cargo.toml
index 3b70ef1..dbc0de1 100644
--- a/sw/host/rom_ext_image_tools/Cargo.toml
+++ b/sw/host/rom_ext_image_tools/signer/Cargo.toml
@@ -19,4 +19,4 @@
 debug = true
 
 [dependencies]
-ring = "0.16.16"
+mundane = "0.4.3"
diff --git a/sw/host/rom_ext_image_tools/signer/meson.build b/sw/host/rom_ext_image_tools/signer/meson.build
new file mode 100644
index 0000000..4c1db78
--- /dev/null
+++ b/sw/host/rom_ext_image_tools/signer/meson.build
@@ -0,0 +1,65 @@
+# Copyright lowRISC contributors.
+# Licensed under the Apache License, Version 2.0, see LICENSE for details.
+# SPDX-License-Identifier: Apache-2.0
+
+cargo = find_program('cargo', required: false, disabler: true)
+
+build_type = 'release'
+build_dir = meson.current_build_dir()
+manifest_path = meson.current_source_dir() / 'Cargo.toml'
+toolchain_file = meson.current_source_dir() / '..' / 'rust-toolchain'
+
+# CARGO FLAGS:
+# These flags will only apply to the final binary, and won't get propogated
+# to the dependency crate builds.
+cargo_flags_array = [
+  'manifest-path=' + manifest_path,
+  'target-dir=' + build_dir,
+   build_type,
+]
+
+cargo_flags = ''
+foreach flag : cargo_flags_array
+  cargo_flags += '--' + flag + ' '
+endforeach
+
+# RUSTFLAGS:
+# These flags will apply to all the dependencies, as well as the final
+# binary. Linker and linker flavor amongst other things can be passed through
+# these flags.
+rust_flags = ''
+
+# The cargo invocation script.
+cargo_invoke_cmd = meson.source_root() / 'util/invoke_cargo.sh'
+
+rom_ext_signer_raw = custom_target(
+  'rom_ext_signer_raw',
+  command: [
+    cargo_invoke_cmd,
+    cargo,
+    cargo_flags,
+    rust_flags,
+    toolchain_file,
+    meson.source_root(),
+    meson.build_root(),
+  ],
+  depend_files: [
+    cargo_invoke_cmd,
+    manifest_path,
+    toolchain_file,
+  ],
+  output: '.',
+  console: true,
+  build_always_stale: true,
+  build_by_default: false,
+)
+
+rom_ext_signer_elf = custom_target(
+  'rom_ext_signer_elf',
+  command: ['cp', '@INPUT@' / build_type / 'rom_ext_signer', '@OUTPUT@'],
+  depends: rom_ext_signer_raw,
+  input: rom_ext_signer_raw,
+  output: 'rom_ext_signer.elf',
+  build_always_stale: true,
+  build_by_default: false,
+)
diff --git a/sw/host/rom_ext_image_tools/src/main.rs b/sw/host/rom_ext_image_tools/signer/src/main.rs
similarity index 100%
rename from sw/host/rom_ext_image_tools/src/main.rs
rename to sw/host/rom_ext_image_tools/signer/src/main.rs