Linux: Allow unbundling brotli to use system library

(cherry picked from commit 153c4a4c4f)

core/SCsub

@@ -65,7 +65,7 @@ thirdparty_misc_sources = [thirdparty_misc_dir + file for file in thirdparty_mis
 env_thirdparty.add_source_files(thirdparty_obj, thirdparty_misc_sources)
 
 # Brotli
-if env["brotli"]:
+if env["brotli"] and env["builtin_brotli"]:
     thirdparty_brotli_dir = "#thirdparty/brotli/"
     thirdparty_brotli_sources = [
         "common/constants.c",

core/io/compression.cpp

@@ -35,13 +35,13 @@
 
 #include "thirdparty/misc/fastlz.h"
 
-#ifdef BROTLI_ENABLED
-#include "thirdparty/brotli/include/brotli/decode.h"
-#endif
-
 #include <zlib.h>
 #include <zstd.h>
 
+#ifdef BROTLI_ENABLED
+#include <brotli/decode.h>
+#endif
+
 int Compression::compress(uint8_t *p_dst, const uint8_t *p_src, int p_src_size, Mode p_mode) {
 	switch (p_mode) {
 		case MODE_BROTLI: {