test(ENG-21524): Fuzzilli Stop-Gap (#24826)

### What does this PR do?

Adds [@mschwarzl's Fuzzilli Support
PR](https://github.com/oven-sh/bun/pull/23862) with the changes
necessary to be able to:

- Run it in CI
- Make no impact on `debug` and `release` mode.

### How did you verify your code works?

---------

Co-authored-by: Martin Schwarzl <mschwarzl@cloudflare.com>
Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
Co-authored-by: Dylan Conway <dylan.conway567@gmail.com>

cmake/CompilerFlags.cmake

@@ -51,6 +51,23 @@ if(ENABLE_ASAN)
   )
 endif()
 
+if(ENABLE_FUZZILLI)
+  register_compiler_flags(
+    DESCRIPTION "Enable coverage instrumentation for fuzzing"
+    -fsanitize-coverage=trace-pc-guard
+  )
+
+  register_linker_flags(
+    DESCRIPTION "Link coverage instrumentation"
+    -fsanitize-coverage=trace-pc-guard
+  )
+
+  register_compiler_flags(
+    DESCRIPTION "Enable fuzzilli-specific code"
+    -DFUZZILLI_ENABLED
+  )
+endif()
+
 # --- Optimization level ---
 if(DEBUG)
   register_compiler_flags(

cmake/Options.cmake

@@ -127,6 +127,8 @@ if (NOT ENABLE_ASAN)
   set(ENABLE_ZIG_ASAN OFF)
 endif()
 
+optionx(ENABLE_FUZZILLI BOOL "If fuzzilli support should be enabled" DEFAULT OFF)
+
 if(RELEASE AND LINUX AND CI AND NOT ENABLE_ASSERTIONS AND NOT ENABLE_ASAN)
   set(DEFAULT_LTO ON)
 else()

cmake/targets/BuildBun.cmake

@@ -695,6 +695,7 @@ register_command(
       -Dcpu=${ZIG_CPU}
       -Denable_logs=$<IF:$<BOOL:${ENABLE_LOGS}>,true,false>
       -Denable_asan=$<IF:$<BOOL:${ENABLE_ZIG_ASAN}>,true,false>
+      -Denable_fuzzilli=$<IF:$<BOOL:${ENABLE_FUZZILLI}>,true,false>
       -Denable_valgrind=$<IF:$<BOOL:${ENABLE_VALGRIND}>,true,false>
       -Duse_mimalloc=$<IF:$<BOOL:${USE_MIMALLOC_AS_DEFAULT_ALLOCATOR}>,true,false>
       -Dllvm_codegen_threads=${LLVM_ZIG_CODEGEN_THREADS}