ci: disable Homebrew's auto cleanup

Lately Homebrew learned to automagically clean up information about
outdated packages during other 'brew' commands, which might be useful
for the avarage user, but is a waste of time in CI build jobs, because
the next build jobs will start from the exact same image containing
the same outdated packages anyway.

Export HOMEBREW_NO_INSTALL_CLEANUP=1 to disable this auto cleanup feature,
shaving off about 20-30s from the time needed to install dependencies
in our macOS build jobs on Travis CI.

Signed-off-by: SZEDER Gábor <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: szeder

ci/install-dependencies.sh

@@ -34,7 +34,7 @@ linux-clang|linux-gcc)
 	popd
 	;;
 osx-clang|osx-gcc)
-	export HOMEBREW_NO_AUTO_UPDATE=1
+	export HOMEBREW_NO_AUTO_UPDATE=1 HOMEBREW_NO_INSTALL_CLEANUP=1
 	# Uncomment this if you want to run perf tests:
 	# brew install gnu-time
 	test -z "$BREW_INSTALL_PACKAGES" ||