Revert "[hwasan] Add fixed_shadow_base flag" (#95435)

Reverts #73980

This broke static hwasan binaries in Android, for some reason the
fixed_shadow_base branch gets taken

Author: fmayer

compiler-rt/lib/hwasan/hwasan_flags.inc

@@ -84,10 +84,3 @@ HWASAN_FLAG(bool, malloc_bisect_dump, false,
 // are untagged before the call.
 HWASAN_FLAG(bool, fail_without_syscall_abi, true,
             "Exit if fail to request relaxed syscall ABI.")
-
-HWASAN_FLAG(
-    uptr, fixed_shadow_base, -1,
-    "If not -1, HWASan will attempt to allocate the shadow at this address, "
-    "instead of choosing one dynamically."
-    "Tip: this can be combined with the compiler option, "
-    "-hwasan-mapping-offset, to optimize the instrumentation.")

compiler-rt/lib/hwasan/hwasan_linux.cpp

@@ -106,12 +106,8 @@ static uptr GetHighMemEnd() {
 }
 
 static void InitializeShadowBaseAddress(uptr shadow_size_bytes) {
-  if (flags()->fixed_shadow_base != (uptr)-1) {
-    __hwasan_shadow_memory_dynamic_address = flags()->fixed_shadow_base;
-  } else {
-    __hwasan_shadow_memory_dynamic_address =
-        FindDynamicShadowStart(shadow_size_bytes);
-  }
+  __hwasan_shadow_memory_dynamic_address =
+      FindDynamicShadowStart(shadow_size_bytes);
 }
 
 static void MaybeDieIfNoTaggingAbi(const char *message) {