Allow building samples without the compiler.

CMakeLists.txt

diff --git a/CMakeLists.txt b/CMakeLists.txt
index ca49b92..8cabb57 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -96,10 +96,6 @@
 # Derived flags based on primary options
 #-------------------------------------------------------------------------------
 
-if(${IREE_BUILD_SAMPLES})
-  set(IREE_BUILD_COMPILER ON CACHE BOOL "Build the IREE compiler for sample projects." FORCE)
-endif()
-
 if(${IREE_BUILD_COMPILER})
   set(IREE_ENABLE_MLIR ON CACHE BOOL "Enable LLVM dependencies if the IREE compiler is build." FORCE)
 endif()
@@ -169,10 +165,15 @@
   VMVX
 )
 
-if(IREE_TARGET_BACKENDS_TO_BUILD STREQUAL "all")
-  set(IREE_TARGET_BACKENDS_TO_BUILD ${IREE_ALL_TARGET_BACKENDS})
+if(${IREE_BUILD_COMPILER})
+  if(IREE_TARGET_BACKENDS_TO_BUILD STREQUAL "all")
+    set(IREE_TARGET_BACKENDS_TO_BUILD ${IREE_ALL_TARGET_BACKENDS})
+  endif()
+  message(STATUS "Building target backends: ${IREE_TARGET_BACKENDS_TO_BUILD}")
+else()
+  set(IREE_TARGET_BACKENDS_TO_BUILD "" CACHE STRING "" FORCE)
+  message(STATUS "Compiler is disabled, building no target backends")
 endif()
-message(STATUS "Building target backends: ${IREE_TARGET_BACKENDS_TO_BUILD}")
 
 # Default every IREE_TARGET_BACKEND_* to OFF
 foreach(_backend ${IREE_ALL_TARGET_BACKENDS})