[compiler-rt][test] Ensure CMAKE_SYSROOT is added as a test cflag if provided

[leonardchan]

Summary

When running tests like SanitizerCommon-asan-x86_64-Linux :: Linux/crypt_r.cpp, it may attempt to use the host header crypt.h rather than a sysroot header. This is significant in the event where struct crypt_data defined on host is different from the sysroot used to make the sanitizer runtime libraries. This can result in logical differences between the expected size/layout of struct crypt_data known by sanitizers and the strict crypt_data provided by the host crypt.h.

Since tests should still use the CMAKE_SYSROOT, this ensures that CMAKE_SYSROOT is propagated to compiler-rt tests.

[phosek]

LGTM

compiler-rt/test/sanitizer_common/CMakeLists.txt

foreach(arch ${TEST_ARCH})
     set(SANITIZER_COMMON_TEST_TARGET_ARCH ${arch})
     get_test_cc_for_arch(${arch} SANITIZER_COMMON_TEST_TARGET_CC SANITIZER_COMMON_TEST_TARGET_CFLAGS)
     set(CONFIG_NAME ${tool}-${arch}-${OS_NAME})
 
     # ARM on Linux might use the slow unwinder as default and the unwind table is
     # required to get a complete stacktrace.
     if ("${CMAKE_SYSTEM_NAME}" STREQUAL "Linux" AND NOT ANDROID)
       list(APPEND SANITIZER_COMMON_TEST_TARGET_CFLAGS -funwind-tables)
+      if(CMAKE_SYSROOT)
+        list(APPEND SANITIZER_COMMON_TEST_TARGET_CFLAGS "--sysroot=${CMAKE_SYSROOT}")
+      endif()
       string(REPLACE ";" " " SANITIZER_COMMON_TEST_TARGET_CFLAGS
                              "${SANITIZER_COMMON_TEST_TARGET_CFLAGS}")
     endif()
 
     configure_lit_site_cfg(
       ${CMAKE_CURRENT_SOURCE_DIR}/lit.site.cfg.py.in
       ${CMAKE_CURRENT_BINARY_DIR}/${CONFIG_NAME}/lit.site.cfg.py)
     # FIXME(dliew): LSan i386 on Darwin is completely broken right now.