change some sys.exit() to be fatal

- when not all freetype deps are builtin (or provided externally)
- when attempting to build on an unsupported CPU architecture

platform/linuxbsd/detect.py

@@ -70,7 +70,7 @@ def configure(env: "Environment"):
             'Unsupported CPU architecture "%s" for Linux / *BSD. Supported architectures are: %s.'
             % (env["arch"], ", ".join(supported_arches))
         )
-        sys.exit()
+        sys.exit(255)
 
     ## Build type
 
@@ -208,7 +208,7 @@ def configure(env: "Environment"):
             "freetype, libpng, zlib, graphite, harfbuzz.\n"
             "Please specify `builtin_<name>=no` for all of them, or none."
         )
-        sys.exit()
+        sys.exit(255)
 
     if not env["builtin_freetype"]:
         env.ParseConfig("pkg-config freetype2 --cflags --libs")