Only install julia binaries into bin/
Install git binaries into $(BUILD)/libexec, instead of $(BUILD)/bin
Don't forget to create $(BUILD)/libexec when we don't already have it
Configure git to install to libexec rather than moving the files manually
Also try to install bin/*.{dll,bat}
Merge pull request #4951 from JuliaLang/sf/bincleanup

Move git to libexec, remove all binaries other than `julia` from bin directory of install targets