Fix opcache path determination, again

We shouldn't be appending to the executable path, but rather to
the directory of the executable.

Author: nikic

sapi/fuzzer/fuzzer-execute-common.h

@@ -138,6 +138,13 @@ ZEND_ATTRIBUTE_UNUSED char *get_opcache_path(void) {
 		ZEND_ASSERT(0 && "Failed to get binary path");
 		return NULL;
 	}
+
+	/* Get basename. */
+	char *last_sep = strrchr(path, '/');
+	if (last_sep) {
+		*last_sep = '\0';
+	}
+
 	strlcat(path, "/modules/opcache.so", sizeof(path));
 	return realpath(path, NULL);
 }

sapi/fuzzer/fuzzer-function-jit.c

@@ -53,7 +53,7 @@ int LLVMFuzzerInitialize(int *argc, char ***argv) {
 	char *opcache_path = get_opcache_path();
 	assert(opcache_path && "Failed to determine opcache path");
 
-	char ini_buf[256];
+	char ini_buf[512];
 	snprintf(ini_buf, sizeof(ini_buf),
 		"zend_extension=%s\n"
 		"opcache.validate_timestamps=0\n"