OSX: Fix linking with osxcross for arm64

For some reason the `-target` option on the `LINKFLAGS` was causing a weird
issue where osxcross' clang wrapper would attempt using the system `/bin/ld`
instead of the osxcross version (which is Apple's `ld64`).

The error message would be:
```
/bin/ld: unrecognized option '-dynamic'
```

Also removed from `CCFLAGS` for consistency, it seems to work fine with only
`-mmacosx-version-min`.

platform/osx/detect.py

@@ -87,8 +87,8 @@ def configure(env):
 
     if env["arch"] == "arm64":
         print("Building for macOS 10.15+, platform arm64.")
-        env.Append(CCFLAGS=["-arch", "arm64", "-mmacosx-version-min=10.15", "-target", "arm64-apple-macos10.15"])
-        env.Append(LINKFLAGS=["-arch", "arm64", "-mmacosx-version-min=10.15", "-target", "arm64-apple-macos10.15"])
+        env.Append(CCFLAGS=["-arch", "arm64", "-mmacosx-version-min=10.15"])
+        env.Append(LINKFLAGS=["-arch", "arm64", "-mmacosx-version-min=10.15"])
     else:
         print("Building for macOS 10.12+, platform x86-64.")
         env.Append(CCFLAGS=["-arch", "x86_64", "-mmacosx-version-min=10.12"])