[CMake] Provide an option to disable runtimes build

This could be used to either disable the runtimes build altogether
or avoid building them but still generate the build targets.

Differential Revision: https://reviews.llvm.org/D31060

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@298653 91177308-0d34-0410-b5e6-96231b3b80d8

CMakeLists.txt

@@ -483,6 +483,10 @@ option(LLVM_INCLUDE_UTILS "Generate build targets for the LLVM utils." ON)
 option(LLVM_BUILD_UTILS
   "Build LLVM utility binaries. If OFF, just generate build targets." ON)
 
+option(LLVM_INCLUDE_RUNTIMES "Generate build targets for the LLVM runtimes." ON)
+option(LLVM_BUILD_RUNTIMES
+  "Build the LLVM runtimes. If OFF, just generate build targets." ON)
+
 option(LLVM_BUILD_RUNTIME
   "Build the LLVM runtime libraries." ON)
 option(LLVM_BUILD_EXAMPLES
@@ -862,7 +866,9 @@ if( LLVM_INCLUDE_TOOLS )
   add_subdirectory(tools)
 endif()
 
-add_subdirectory(runtimes)
+if( LLVM_INCLUDE_RUNTIMES )
+  add_subdirectory(runtimes)
+endif()
 
 if( LLVM_INCLUDE_EXAMPLES )
   add_subdirectory(examples)

runtimes/CMakeLists.txt

@@ -145,6 +145,10 @@ else() # if this is included from LLVM's CMake
   set_property(DIRECTORY APPEND PROPERTY CMAKE_CONFIGURE_DEPENDS ${LLVM_BINARY_DIR}/runtimes/Components.cmake)
   include(LLVMExternalProjectUtils)
 
+  if(NOT LLVM_BUILD_RUNTIMES)
+    set(EXTRA_ARGS EXCLUDE_FROM_ALL)
+  endif()
+
   # If compiler-rt is present we need to build the builtin libraries first. This
   # is required because the other runtimes need the builtin libraries present
   # before the just-built compiler can pass the configuration tests.
@@ -157,7 +161,8 @@ else() # if this is included from LLVM's CMake
                                           -DCMAKE_C_COMPILER_TARGET=${TARGET_TRIPLE}
                                           -DCMAKE_ASM_COMPILER_TARGET=${TARGET_TRIPLE}
                                PASSTHROUGH_PREFIXES COMPILER_RT
-                               USE_TOOLCHAIN)
+                               USE_TOOLCHAIN
+                               ${EXTRA_ARGS})
     else()
       get_cmake_property(variableNames VARIABLES)
       add_custom_target(builtins)
@@ -179,7 +184,8 @@ else() # if this is included from LLVM's CMake
                                           -DCOMPILER_RT_DEFAULT_TARGET_ONLY=On
                                           ${${target}_extra_args}
                                PASSTHROUGH_PREFIXES COMPILER_RT
-                               USE_TOOLCHAIN)
+                               USE_TOOLCHAIN
+                               ${EXTRA_ARGS})
         add_dependencies(builtins builtins-${target})
       endforeach()
     endif()
@@ -238,7 +244,8 @@ else() # if this is included from LLVM's CMake
                                             ${SUB_COMPONENTS}
                                             ${SUB_COMPONENT_CHECK_TARGETS}
                                             ${SUB_INSTALL_TARGETS}
-                             USE_TOOLCHAIN)
+                             USE_TOOLCHAIN
+                             ${EXTRA_ARGS})
 
     # TODO: This is a hack needed because the libcxx headers are copied into the
     # build directory during configuration. Without that step the clang in the