add cs profiling as optional second step profiling pass

src/globals/patch/spc_pgo_flush_php_main.patch

@@ -1,13 +1,10 @@
 --- a/main/main.c
 +++ b/main/main.c
-@@ -2563,6 +2563,12 @@
+@@ -2563,6 +2563,9 @@
  #endif
 
  	zend_observer_shutdown();
 +
-+	/* spc-pgo: explicit profile flush so embed/frankenphp callers that exit
-+	 * via SYS_exit_group (skipping libc atexit) still get .profraw written.
-+	 * Weak symbol → no-op in non-PGO builds. */
 +	{ extern int __llvm_profile_write_file(void) __attribute__((weak));
 +	  if (__llvm_profile_write_file) __llvm_profile_write_file(); }
  }