ci: stop linking built-ins to the dashed versions

Originally, all of Git's subcommands were implemented in their own
executable/script, using the naming scheme `git-<command-name>`. When
more and more functionality was turned into built-in commands (i.e. the
`git` executable could run them without spawning a separate process),
for backwards-compatibility, we hard-link the `git` executable to
`git-<built-in>` for every built-in.

This backwards-compatibility was needed to support scripts that called
the dashed form, even if we deprecated that a _long_ time ago.

For that reason, we just introduced a Makefile knob to skip linking
them. TO make sure that this keeps working, teach the CI
(and PR) builds to skip generating those hard-links.

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho

ci/run-build-and-tests.sh

@@ -10,7 +10,7 @@ windows*) cmd //c mklink //j t\\.prove "$(cygpath -aw "$cache_dir/.prove")";;
 *) ln -s "$cache_dir/.prove" t/.prove;;
 esac
 
-make
+make SKIP_DASHED_BUILT_INS=YesPlease
 case "$jobname" in
 linux-gcc)
 	make test