Standardization pass through docs/ folder.  (#3597)

* recommend an out-of-tree CMake build directory `../iree-build/` instead of in-tree `build/`
* consistently use `.vmfb` as VM module flatbuffer file extensions
* make some docs use CMake examples instead of Bazel examples
* prefix all shell commands with `$`
* indent shell commands two spaces when continuing onto multiple lines
* consistently use `-` for LLVM flags and `--` for Abseil flags
* typo fixes
diff --git a/docs/get_started/getting_started_linux_vulkan.md b/docs/get_started/getting_started_linux_vulkan.md
index 28a54f4..951ee38 100644
--- a/docs/get_started/getting_started_linux_vulkan.md
+++ b/docs/get_started/getting_started_linux_vulkan.md
@@ -47,8 +47,8 @@
 ```shell
 # -- CMake --
 $ export VK_LOADER_DEBUG=all
-$ cmake --build build/ --target iree_hal_vulkan_dynamic_symbols_test
-$ ./build/iree/hal/vulkan/iree_hal_vulkan_dynamic_symbols_test
+$ cmake --build ../iree-build/ --target iree_hal_vulkan_dynamic_symbols_test
+$ ../iree-build/iree/hal/vulkan/iree_hal_vulkan_dynamic_symbols_test
 
 # -- Bazel --
 $ bazel test iree/hal/vulkan:dynamic_symbols_test --test_env=VK_LOADER_DEBUG=all
@@ -63,8 +63,8 @@
 ```shell
 # -- CMake --
 $ export VK_LOADER_DEBUG=all
-$ cmake --build build/ --target iree_hal_cts_driver_test
-$ ./build/iree/hal/cts/iree_hal_cts_driver_test
+$ cmake --build ../iree-build/ --target iree_hal_cts_driver_test
+$ ../iree-build/iree/hal/cts/iree_hal_cts_driver_test
 
 # -- Bazel --
 $ bazel test iree/hal/cts:driver_test --test_env=VK_LOADER_DEBUG=all --test_output=all
@@ -115,11 +115,11 @@
 
 ```shell
 # -- CMake --
-$ cmake --build build/ --target iree_tools_iree-translate
-$ ./build/iree/tools/iree-translate -iree-mlir-to-vm-bytecode-module -iree-hal-target-backends=vulkan-spirv ./iree/tools/test/simple.mlir -o /tmp/module.fb
+$ cmake --build ../iree-build/ --target iree_tools_iree-translate
+$ ../iree-build/iree/tools/iree-translate -iree-mlir-to-vm-bytecode-module -iree-hal-target-backends=vulkan-spirv ./iree/tools/test/simple.mlir -o /tmp/module.vmfb
 
 # -- Bazel --
-$ bazel run iree/tools:iree-translate -- -iree-mlir-to-vm-bytecode-module -iree-hal-target-backends=vulkan-spirv $PWD/iree/tools/test/simple.mlir -o /tmp/module.fb
+$ bazel run iree/tools:iree-translate -- -iree-mlir-to-vm-bytecode-module -iree-hal-target-backends=vulkan-spirv $PWD/iree/tools/test/simple.mlir -o /tmp/module.vmfb
 ```
 
 > Tip:<br>
@@ -132,11 +132,11 @@
 
 ```shell
 # -- CMake --
-$ cmake --build build/ --target iree_tools_iree-run-module
-$ ./build/iree/tools/iree-run-module -module_file=/tmp/module.fb -driver=vulkan -entry_function=abs -function_inputs="i32=-2"
+$ cmake --build ../iree-build/ --target iree_tools_iree-run-module
+$ ../iree-build/iree/tools/iree-run-module -module_file=/tmp/module.vmfb -driver=vulkan -entry_function=abs -function_inputs="i32=-2"
 
 # -- Bazel --
-$ bazel run iree/tools:iree-run-module -- -module_file=/tmp/module.fb -driver=vulkan -entry_function=abs -function_inputs="i32=-2"
+$ bazel run iree/tools:iree-run-module -- -module_file=/tmp/module.vmfb -driver=vulkan -entry_function=abs -function_inputs="i32=-2"
 ```
 
 ## Running IREE's Vulkan Samples
@@ -145,8 +145,8 @@
 
 ```shell
 # -- CMake --
-$ cmake --build build/ --target iree_samples_vulkan_vulkan_inference_gui
-$ ./build/iree/samples/vulkan/vulkan_inference_gui
+$ cmake --build ../iree-build/ --target iree_samples_vulkan_vulkan_inference_gui
+$ ../iree-build/iree/samples/vulkan/vulkan_inference_gui
 
 # -- Bazel --
 $ bazel run iree/samples/vulkan:vulkan_inference_gui