[compiler-rt] Add CMake flag for AArch64 Linux with 39-bit VA.

Sanitizers currently assume AArch64 Linux has 48-bit VA.  Followup
patches will add checks for this flag to asan and hwasan.

Author: efriedma-quic

compiler-rt/CMakeLists.txt

@@ -290,6 +290,9 @@ option(SANITIZER_USE_STATIC_TEST_CXX
   "Use static libc++ for tests." ${DEFAULT_SANITIZER_USE_STATIC_TEST_CXX})
 pythonize_bool(SANITIZER_USE_STATIC_TEST_CXX)
 
+option(SANITIZER_AARCH64_39BIT_VA
+  "Configure sanitizer allocator for 39-bit VA kernel." OFF)
+
 set(COMPILER_RT_SUPPORTED_CXX_LIBRARIES none default libcxx)
 set(COMPILER_RT_CXX_LIBRARY "default" CACHE STRING "Specify C++ library to use. Supported values are ${COMPILER_RT_SUPPORTED_CXX_LIBRARIES}.")
 if (NOT "${COMPILER_RT_CXX_LIBRARY}" IN_LIST COMPILER_RT_SUPPORTED_CXX_LIBRARIES)
@@ -843,6 +846,10 @@ if (SANITIZER_DISABLE_SYMBOLIZER_PATH_SEARCH)
   add_compile_definitions(SANITIZER_DISABLE_SYMBOLIZER_PATH_SEARCH)
 endif()
 
+if (SANITIZER_AARCH64_39BIT_VA)
+  add_compile_definitions(SANITIZER_AARCH64_39BIT_VA)
+endif()
+
 add_subdirectory(lib)
 
 if(COMPILER_RT_INCLUDE_TESTS)