Introduce hwasan mode for linker

This mode instructs the linker to search for libraries in hwasan
subdirectories of all library search paths. This is set up to contain a
hwasan-enabled copy of libc, which is needed for HWASan programs to
operate. There are two ways this mode can be enabled:

* for native binaries, by using the linker_hwasan64 symlink as its
  interpreter
* for apps: by setting the LD_HWASAN environment variable in wrap.sh

Bug: 276930343
Change-Id: I0f4117a50091616f26947fbe37a28ee573b97ad0
diff --git a/linker/Android.bp b/linker/Android.bp
index 83077c6..020bd7d 100644
--- a/linker/Android.bp
+++ b/linker/Android.bp
@@ -374,6 +374,11 @@
     ],
 
     symlinks: ["linker_asan"],
+    arch: {
+        arm64: {
+            symlinks: ["linker_hwasan"],
+        },
+    },
     multilib: {
         lib64: {
             suffix: "64",