Index: compiler-rt/CMakeLists.txt
===================================================================
--- compiler-rt/CMakeLists.txt
+++ compiler-rt/CMakeLists.txt
@@ -570,6 +570,14 @@
 
 # Unittests need access to C++ standard library.
 string(APPEND COMPILER_RT_TEST_COMPILER_CFLAGS " ${stdlib_flag}")
+# CMAKE_SYSROOT instructs cmake to pass `--sysroot=${CMAKE_SYSROOT}` to compile
+# and link steps. For normal cmake targets we don't need to do anything, but for
+# lit tests we need to manually add this flag to the compilation options.
+# This isn't done here for Apple platforms where sysroot handling is more
+# nuanced. See `find_darwin_sdk_dir` and `darwin_add_builtin_library`.
+if (NOT APPLE AND (COMPILER_RT_HAS_SYSROOT_FLAG AND CMAKE_SYSROOT))
+  string(APPEND COMPILER_RT_TEST_COMPILER_CFLAGS " --sysroot=${CMAKE_SYSROOT}")
+endif()
 
 # When cross-compiling, COMPILER_RT_TEST_COMPILER_CFLAGS help in compilation
 # and linking of unittests.
Index: compiler-rt/lib/tsan/go/buildgo.sh
===================================================================
--- compiler-rt/lib/tsan/go/buildgo.sh
+++ compiler-rt/lib/tsan/go/buildgo.sh
@@ -220,7 +220,7 @@
 fi
 $CC $DIR/gotsan.cpp -c -o $DIR/race_$SUFFIX.syso $FLAGS $CFLAGS
 
-$CC $OSCFLAGS $ARCHCFLAGS test.c $DIR/race_$SUFFIX.syso -g -o $DIR/test $OSLDFLAGS $LDFLAGS
+$CC $OSCFLAGS $ARCHCFLAGS test.c $DIR/race_$SUFFIX.syso -g -o $DIR/test $OSLDFLAGS $LDFLAGS $EXTRA_CFLAGS
 
 # Verify that no libc specific code is present.
 if [ "$DEPENDS_ON_LIBC" != "1" ]; then
Index: compiler-rt/lib/tsan/rtl/CMakeLists.txt
===================================================================
--- compiler-rt/lib/tsan/rtl/CMakeLists.txt
+++ compiler-rt/lib/tsan/rtl/CMakeLists.txt
@@ -114,6 +114,8 @@
 if("${CMAKE_C_FLAGS}" MATCHES "-Wno-(error=)?unused-command-line-argument")
   set(EXTRA_CFLAGS "-Wno-error=unused-command-line-argument ${EXTRA_CFLAGS}")
 endif()
+# Make sure the flags in COMPILER_RT_TEST_COMPILER_CFLAGS are also used by buildgo.sh.
+set(EXTRA_CFLAGS "${COMPILER_RT_TEST_COMPILER_CFLAGS} ${EXTRA_CFLAGS}")
 
 if(APPLE)
   # Ideally we would check the SDK version for the actual platform we are
Index: compiler-rt/test/fuzzer/lit.cfg.py
===================================================================
--- compiler-rt/test/fuzzer/lit.cfg.py
+++ compiler-rt/test/fuzzer/lit.cfg.py
@@ -75,7 +75,7 @@
 
 def generate_compiler_cmd(is_cpp=True, fuzzer_enabled=True, msan_enabled=False):
     compiler_cmd = config.clang
-    extra_cmd = config.target_flags
+    extra_cmd = config.target_flags + config.target_cflags
 
     if is_cpp:
         std_cmd = "--driver-mode=g++"
Index: compiler-rt/test/lit.common.configured.in
===================================================================
--- compiler-rt/test/lit.common.configured.in
+++ compiler-rt/test/lit.common.configured.in
@@ -7,7 +7,6 @@
 
 # Generic config options for all compiler-rt lit tests.
 set_default("target_triple", "@COMPILER_RT_DEFAULT_TARGET_TRIPLE@")
-set_default("target_cflags", "@COMPILER_RT_TEST_COMPILER_CFLAGS@")
 set_default("host_arch", "@HOST_ARCH@")
 set_default("target_arch", "@COMPILER_RT_DEFAULT_TARGET_ARCH@")
 set_default("host_os", "@HOST_OS@")
@@ -68,6 +67,9 @@
 set_default("have_zlib", @ZLIB_FOUND_PYBOOL@)
 set_default("libcxx_used", "@LLVM_LIBCXX_USED@")
 
+target_cflags = getattr(config, "target_cflags", "")
+setattr(config, "target_cflags", target_cflags + " @COMPILER_RT_TEST_COMPILER_CFLAGS@")
+
 # LLVM tools dir can be passed in lit parameters, so try to
 # apply substitution.
 config.llvm_tools_dir = lit_config.substitute(config.llvm_tools_dir)
Index: compiler-rt/test/safestack/lit.cfg.py
===================================================================
--- compiler-rt/test/safestack/lit.cfg.py
+++ compiler-rt/test/safestack/lit.cfg.py
@@ -13,10 +13,16 @@
 
 # Add clang substitutions.
 config.substitutions.append(
-    ("%clang_nosafestack ", config.clang + " -O0 -fno-sanitize=safe-stack ")
+    (
+        "%clang_nosafestack ",
+        config.clang + config.target_cflags + " -O0 -fno-sanitize=safe-stack ",
+    )
 )
 config.substitutions.append(
-    ("%clang_safestack ", config.clang + " -O0 -fsanitize=safe-stack ")
+    (
+        "%clang_safestack ",
+        config.clang + config.target_cflags + " -O0 -fsanitize=safe-stack ",
+    )
 )
 
 if config.lto_supported: