[compiler-rt] Add option to disable libc++ build

Having libc++ checked out doesn't necessarily mean it should be built;
for example, the same source tree might be used for multiple build
configurations, and libc++ might not build in some of those
configurations. Add an option to compiler-rt's build to disable building
libc++. This defaults to ON, so it shouldn't change any existing build
configurations.

Differential Revision: https://reviews.llvm.org/D56479

llvm-svn: 351117

diff --git a/compiler-rt/CMakeLists.txt b/compiler-rt/CMakeLists.txt
index ab69c51..aa360a3 100644 (file)
--- a/compiler-rt/CMakeLists.txt
+++ b/compiler-rt/CMakeLists.txt
@@ -428,15 +428,19 @@ endif()
 
 add_subdirectory(include)
 
-foreach(path IN ITEMS ${LLVM_MAIN_SRC_DIR}/projects/libcxx
-                      ${LLVM_MAIN_SRC_DIR}/runtimes/libcxx
-                      ${LLVM_MAIN_SRC_DIR}/../libcxx
-                      ${LLVM_EXTERNAL_LIBCXX_SOURCE_DIR})
-  if(IS_DIRECTORY ${path})
-    set(COMPILER_RT_LIBCXX_PATH ${path})
-    break()
-  endif()
-endforeach()
+option(COMPILER_RT_USE_LIBCXX
+  "Enable compiler-rt to use libc++ from the source tree" ON)
+if(COMPILER_RT_USE_LIBCXX)
+  foreach(path IN ITEMS ${LLVM_MAIN_SRC_DIR}/projects/libcxx
+                        ${LLVM_MAIN_SRC_DIR}/runtimes/libcxx
+                        ${LLVM_MAIN_SRC_DIR}/../libcxx
+                        ${LLVM_EXTERNAL_LIBCXX_SOURCE_DIR})
+    if(IS_DIRECTORY ${path})
+      set(COMPILER_RT_LIBCXX_PATH ${path})
+      break()
+    endif()
+  endforeach()
+endif()
 
 set(COMPILER_RT_LLD_PATH ${LLVM_MAIN_SRC_DIR}/tools/lld)
 if(EXISTS ${COMPILER_RT_LLD_PATH}/ AND LLVM_TOOL_LLD_BUILD)