diff --git a/compiler-rt/CMakeLists.txt b/compiler-rt/CMakeLists.txt
--- a/compiler-rt/CMakeLists.txt
+++ b/compiler-rt/CMakeLists.txt
@@ -185,7 +185,11 @@
 pythonize_bool(SANITIZER_CAN_USE_CXXABI)
 
 macro(handle_default_cxx_lib var)
-  if (${var} STREQUAL "default")
+  # Specifying -stdlib= in CMAKE_CXX_FLAGS overrides the defaults.
+  if (CMAKE_CXX_FLAGS MATCHES "-stdlib=([a-zA-Z+]*)")
+    set(${var}_LIBNAME "${CMAKE_MATCH_1}")
+    set(${var}_SYSTEM 1)
+  elseif (${var} STREQUAL "default")
     if (APPLE OR CMAKE_SYSTEM_NAME MATCHES "FreeBSD")
       set(${var}_LIBNAME "libc++")
       set(${var}_SYSTEM 1)
@@ -439,6 +443,25 @@
   list(APPEND SANITIZER_COMMON_LINK_LIBS zircon)
 endif()
 
+# TODO: COMPILER_RT_COMMON_CFLAGS and COMPILER_RT_COMMON_LINK_FLAGS are
+# intended for use in non-sanitizer runtimes such as libFuzzer, profile or XRay,
+# move these higher to include common flags, then derive SANITIZER_COMMON_CFLAGS
+# and SANITIZER_COMMON_LINK_FLAGS from those and append sanitizer-specific flags.
+set(COMPILER_RT_COMMON_CFLAGS ${SANITIZER_COMMON_CFLAGS})
+set(COMPILER_RT_COMMON_LINK_FLAGS ${SANITIZER_COMMON_LINK_FLAGS})
+
+# We don't use the C++ standard library, so avoid including it by mistake.
+append_list_if(COMPILER_RT_HAS_NOSTDINCXX_FLAG -nostdinc++ SANITIZER_COMMON_CFLAGS)
+append_list_if(COMPILER_RT_HAS_NOSTDLIBXX_FLAG -nostdlib++ SANITIZER_COMMON_LINK_FLAGS)
+
+# Remove -stdlib= which is unused when passing -nostdinc++...
+string(REGEX MATCHALL "-stdlib=[a-zA-Z+]*" stdlib_flag ${CMAKE_CXX_FLAGS})
+string(REGEX REPLACE "-stdlib=[a-zA-Z+]*" "" CMAKE_CXX_FLAGS ${CMAKE_CXX_FLAGS})
+
+# ...we need it to build some runtimes and tests so readd it where appropriate.
+list(APPEND COMPILER_RT_COMMON_CFLAGS ${stdlib_flag})
+list(APPEND COMPILER_RT_COMMON_LINK_FLAGS ${stdlib_flag})
+
 macro(append_libcxx_libs var)
   if (${var}_INTREE)
     if (SANITIZER_USE_STATIC_LLVM_UNWINDER AND (TARGET unwind_static OR HAVE_LIBUNWIND))
@@ -471,8 +494,14 @@
   append_list_if(COMPILER_RT_HAS_LIBSTDCXX stdc++ SANITIZER_TEST_CXX_LIBRARIES)
 endif()
 
-# when cross compiling, COMPILER_RT_TEST_COMPILER_CFLAGS help
-# in compilation and linking of unittests.
+# TODO: There's a lot of duplication across lib/*/tests/CMakeLists.txt files,
+# move some of the common flags to COMPILER_RT_UNITTEST_CFLAGS.
+
+# Unittests need access to C++ standard library.
+string(APPEND COMPILER_RT_TEST_COMPILER_CFLAGS " ${stdlib_flag}")
+
+# When cross-compiling, COMPILER_RT_TEST_COMPILER_CFLAGS help in compilation
+# and linking of unittests.
 string(REPLACE " " ";" COMPILER_RT_UNITTEST_CFLAGS "${COMPILER_RT_TEST_COMPILER_CFLAGS}")
 set(COMPILER_RT_UNITTEST_LINK_FLAGS ${COMPILER_RT_UNITTEST_CFLAGS})
 
diff --git a/compiler-rt/lib/fuzzer/CMakeLists.txt b/compiler-rt/lib/fuzzer/CMakeLists.txt
--- a/compiler-rt/lib/fuzzer/CMakeLists.txt
+++ b/compiler-rt/lib/fuzzer/CMakeLists.txt
@@ -55,14 +55,13 @@
   }
   " HAS_THREAD_LOCAL)
 
-set(LIBFUZZER_CFLAGS ${SANITIZER_COMMON_CFLAGS})
+set(LIBFUZZER_CFLAGS ${COMPILER_RT_COMMON_CFLAGS})
 
 if(OS_NAME MATCHES "Linux|Fuchsia" AND
    COMPILER_RT_LIBCXX_PATH AND
    COMPILER_RT_LIBCXXABI_PATH)
-  list(APPEND LIBFUZZER_CFLAGS -nostdinc++ -D_LIBCPP_ABI_VERSION=Fuzzer)
-  # Remove -stdlib= which is unused when passing -nostdinc++.
-  string(REGEX REPLACE "-stdlib=[a-zA-Z+]*" "" CMAKE_CXX_FLAGS ${CMAKE_CXX_FLAGS})
+  list(APPEND LIBFUZZER_CFLAGS -D_LIBCPP_ABI_VERSION=Fuzzer)
+  append_list_if(COMPILER_RT_HAS_NOSTDINCXX_FLAG -nostdinc++ LIBFUZZER_CFLAGS)
 elseif(TARGET cxx-headers OR HAVE_LIBCXX)
   # libFuzzer uses C++ standard library headers.
   set(LIBFUZZER_DEPS cxx-headers)
diff --git a/compiler-rt/lib/sanitizer_common/tests/CMakeLists.txt b/compiler-rt/lib/sanitizer_common/tests/CMakeLists.txt
--- a/compiler-rt/lib/sanitizer_common/tests/CMakeLists.txt
+++ b/compiler-rt/lib/sanitizer_common/tests/CMakeLists.txt
@@ -210,9 +210,7 @@
       $<TARGET_OBJECTS:RTSanitizerCommon.${arch}>
       $<TARGET_OBJECTS:RTSanitizerCommonLibc.${arch}>
       $<TARGET_OBJECTS:RTSanitizerCommonSymbolizer.${arch}>)
-    set_target_compile_flags(SanitizerTest
-      ${SANITIZER_COMMON_CFLAGS}
-      ${SANITIZER_TEST_CFLAGS_COMMON})
+    set_target_compile_flags(SanitizerTest ${SANITIZER_TEST_CFLAGS_COMMON})
     # Setup correct output directory and link flags.
     set_target_properties(SanitizerTest PROPERTIES
       RUNTIME_OUTPUT_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR})
diff --git a/compiler-rt/lib/xray/CMakeLists.txt b/compiler-rt/lib/xray/CMakeLists.txt
--- a/compiler-rt/lib/xray/CMakeLists.txt
+++ b/compiler-rt/lib/xray/CMakeLists.txt
@@ -132,7 +132,7 @@
 include_directories(..)
 include_directories(../../include)
 
-set(XRAY_CFLAGS ${SANITIZER_COMMON_CFLAGS})
+set(XRAY_CFLAGS ${COMPILER_RT_COMMON_CFLAGS})
 set(XRAY_COMMON_DEFINITIONS XRAY_HAS_EXCEPTIONS=1)
 
 # We don't need RTTI in XRay, so turn that off.