CI: Use ccache to speed up the build

Speeds up recompilation by caching previous compilations and detecting
when the same compilation is being done again. [skip appveyor]

CI/install-dependencies-osx.sh

@@ -13,8 +13,11 @@ sudo installer -pkg ./Packages.pkg -target /
 
 brew update
 
-#Base OBS Deps
-brew install qt5 jack speexdsp
+#Base OBS Deps and ccache
+brew install qt5 jack speexdsp ccache
+
+export PATH=/usr/local/opt/ccache/libexec:$PATH
+ccache -s || echo "CCache is not available."
 
 # Fetch and untar prebuilt OBS deps that are compatible with older versions of OSX
 curl -L -O https://s3-us-west-2.amazonaws.com/obs-nightly/osx-deps.tar.gz -f --retry 5 -C -