CMakeFindFrameworks: Fix Brew 'Frameworks' path on Apple Silicon

This approach is compatible with both Intel and Apple Silicon
architectures.

`/usr/local/Frameworks` was added in commit 9970cdcb59
(CMakeFindFrameworks: Allow custom framework locations, 2016-07-30,
v3.7.0-rc1~296^2) unconditionally, but does not work on Apple Silicon.

```
x86_64 (Intel macOS):
$ brew --prefix
/usr/local

arm64 (Apple Silicon macOS):
$ brew --prefix
/opt/homebrew
```
1 file changed