Add buildroot compatibility for HWASAN. (flutter#167133)

Needed to roll https://dart-review.googlesource.com/c/sdk/+/421180.

Author: rmacnak-google

engine/src/build/config/BUILDCONFIG.gn

@@ -143,6 +143,10 @@ declare_args() {
   # Compile for Address Sanitizer to find memory bugs.
   is_asan = false
 
+  # Compile with HWAddress Sanitizer to find memory bugs.
+  # Requires ARM64 hardware
+  is_hwasan = false
+
   # Compile for Leak Sanitizer to find leaks.
   is_lsan = false
 
@@ -319,7 +323,7 @@ default_library_type = "static_library"
 
 # These Sanitizers all imply using the Clang compiler. On Windows they either
 # don't work or work differently.
-using_sanitizer = !is_win && (is_asan || is_lsan || is_tsan || is_msan)
+using_sanitizer = !is_win && (is_asan || is_hwasan || is_lsan || is_tsan || is_msan)
 if (!is_clang && using_sanitizer) {
   is_clang = true
 }
@@ -413,7 +417,7 @@ if (symbol_level == -1) {
   # size is paramount.
   if (is_debug || (!is_linux && !is_wasm)) {
     symbol_level = 2
-  } else if (is_asan || is_lsan || is_tsan || is_msan) {
+  } else if (is_asan || is_hwasan || is_lsan || is_tsan || is_msan) {
     # Sanitizers require symbols for filename suppressions to work.
     symbol_level = 1
   } else {

engine/src/build/config/compiler/BUILD.gn

@@ -125,6 +125,10 @@ config("compiler") {
       cflags += [ "-fsanitize=address" ]
       ldflags += [ "-fsanitize=address" ]
     }
+    if (is_hwasan && is_android && current_cpu == "arm64") {
+      cflags += [ "-fsanitize=hwaddress" ]
+      ldflags += [ "-fsanitize=hwaddress" ]
+    }
     if (is_lsan) {
       cflags += [ "-fsanitize=leak" ]
       ldflags += [ "-fsanitize=leak" ]

engine/src/build/config/sanitizers/BUILD.gn

@@ -10,7 +10,7 @@ import("//build/toolchain/toolchain.gni")
 # shared_libraries. Unconditionally depend upon this target as it is empty if
 # |is_asan|, |is_lsan|, |is_tsan|, |is_msan| and |use_custom_libcxx| are false.
 group("deps") {
-  if (is_asan || is_lsan || is_tsan || is_msan) {
+  if (is_asan || is_hwasan || is_lsan || is_tsan || is_msan) {
     public_configs = [ ":sanitizer_options_link_helper" ]
     deps += [ ":options_sources" ]
   }
@@ -24,6 +24,9 @@ config("sanitizer_options_link_helper") {
   if (is_asan) {
     ldflags += [ "-fsanitize=address" ]
   }
+  if (is_hwasan && is_android && current_cpu == "arm64") {
+    ldflags += [ "-fsanitize=hwaddress" ]
+  }
   if (is_lsan) {
     ldflags += [ "-fsanitize=leak" ]
   }