diff --git a/compiler-rt/lib/gwp_asan/CMakeLists.txt b/compiler-rt/lib/gwp_asan/CMakeLists.txt
--- a/compiler-rt/lib/gwp_asan/CMakeLists.txt
+++ b/compiler-rt/lib/gwp_asan/CMakeLists.txt
@@ -39,7 +39,7 @@
 # append_list_if(COMPILER_RT_HAS_SANITIZER_COMMON ${SANITIZER_COMMON_CFLAGS} GWP_ASAN_CFLAGS)
 
 # Remove -stdlib= which is unused when passing -nostdinc++.
-string(REGEX REPLACE "-stdlib=[a-zA-Z+]*" "" CMAKE_CXX_FLAGS ${CMAKE_CXX_FLAGS})
+string(REGEX REPLACE "-stdlib=[a-zA-Z+]*" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
 
 # Options parsing support is optional. This is an optional library that can be
 # used by an allocator to automatically parse GwpAsan options from the
diff --git a/compiler-rt/lib/profile/CMakeLists.txt b/compiler-rt/lib/profile/CMakeLists.txt
--- a/compiler-rt/lib/profile/CMakeLists.txt
+++ b/compiler-rt/lib/profile/CMakeLists.txt
@@ -113,7 +113,7 @@
 # We don't use the C++ Standard Library here, so avoid including it by mistake.
 append_list_if(COMPILER_RT_HAS_NOSTDINCXX_FLAG -nostdinc++ EXTRA_FLAGS)
 # XRay uses C++ standard library headers.
-string(REGEX REPLACE "-stdlib=[a-zA-Z+]*" "" CMAKE_CXX_FLAGS ${CMAKE_CXX_FLAGS})
+string(REGEX REPLACE "-stdlib=[a-zA-Z+]*" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
 
 # This appears to be a C-only warning banning the use of locals in aggregate
 # initializers. All other compilers accept this, though.
diff --git a/compiler-rt/lib/scudo/standalone/CMakeLists.txt b/compiler-rt/lib/scudo/standalone/CMakeLists.txt
--- a/compiler-rt/lib/scudo/standalone/CMakeLists.txt
+++ b/compiler-rt/lib/scudo/standalone/CMakeLists.txt
@@ -11,7 +11,7 @@
   -nostdinc++)
 
 # Remove -stdlib= which is unused when passing -nostdinc++.
-string(REGEX REPLACE "-stdlib=[a-zA-Z+]*" "" CMAKE_CXX_FLAGS ${CMAKE_CXX_FLAGS})
+string(REGEX REPLACE "-stdlib=[a-zA-Z+]*" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
 
 append_list_if(COMPILER_RT_HAS_FVISIBILITY_HIDDEN_FLAG -fvisibility=hidden SCUDO_CFLAGS)