[cmake] Try to appease the buildbots.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@262340 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/runtime/CMakeLists.txt b/runtime/CMakeLists.txt
index 26d6c1233cb57a23366a9c17b29aff0d4ab41443..99298e11b1d74ad908aca2af7f8661e4d568e1e2 100644 (file)
--- a/runtime/CMakeLists.txt
+++ b/runtime/CMakeLists.txt
@@ -27,7 +27,10 @@ set(COMPILER_RT_SRC_ROOT ${LLVM_MAIN_SRC_DIR}/projects/compiler-rt)
 # This is the same behavior (try "internal", then check the LLVM_EXTERNAL_...
 # variable) as in add_llvm_external_project
 if(NOT EXISTS ${COMPILER_RT_SRC_ROOT})
-  set(COMPILER_RT_SRC_ROOT ${LLVM_EXTERNAL_COMPILER_RT_SOURCE_DIR})
+  # We don't want to set it if LLVM_EXTERNAL_COMPILER_RT_SOURCE_DIR is ""
+  if(${LLVM_EXTERNAL_COMPILER_RT_SOURCE_DIR})
+    set(COMPILER_RT_SRC_ROOT ${LLVM_EXTERNAL_COMPILER_RT_SOURCE_DIR})
+  endif()
 endif()
 
 if(LLVM_BUILD_EXTERNAL_COMPILER_RT AND EXISTS ${COMPILER_RT_SRC_ROOT}/)