[PATCH] travis-ci: avoid new tcl/tk build requirement

[Todd Zullinger <tmz@pobox.com>]

A build requirement on tcl/tk was added in 01c54284f1 (Makefile: check
that tcl/tk is installed, 2017-11-20).  For building and running the
tests, we don't need tcl/tk installed.  Bypass the requirement.

Signed-off-by: Todd Zullinger <tmz@pobox.com>
---

Junio C Hamano wrote:
> It seems that TravisCI objects ;-)
>
>    https://travis-ci.org/git/git/jobs/307745929

Interesting that the main builds passed.  I don't know what the default
64-bit linuxinstall looks like in travis, so I presume it includes
tcl/tk or something.

In any case, perhaps something like this is what we want?  We could use
NO_TCLTK or ensure that tcl/tk is installed in all environments.  I used
the BYPASS_TCLTK_CHECK option since the tests have been running without
tcl/tk previously.  If they become required for the tests, this can be
adjusted.

I have a travis job running with this change here:

    https://travis-ci.org/tmzullinger/git/builds/308452464

So far the only failure is (what looks like) an unrelated one in the
GETTEXT_POISON build.

 .travis.yml              | 1 +
 ci/run-linux32-docker.sh | 1 +
 2 files changed, 2 insertions(+)

diff --git a/.travis.yml b/.travis.yml
index 281f101f31..9e57caa83d 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -23,6 +23,7 @@ addons:
 
 env:
   global:
+    - BYPASS_TCLTK_CHECK=1
     - DEVELOPER=1
     # The Linux build installs the defined dependency versions below.
     # The OS X build installs the latest available versions. Keep that
diff --git a/ci/run-linux32-docker.sh b/ci/run-linux32-docker.sh
index 0edf63acfa..8c2b32f7b3 100755
--- a/ci/run-linux32-docker.sh
+++ b/ci/run-linux32-docker.sh
@@ -13,6 +13,7 @@ docker pull daald/ubuntu32:xenial
 
 docker run \
 	--interactive \
+	--env BYPASS_TCLTK_CHECK \
 	--env DEVELOPER \
 	--env DEFAULT_TEST_TARGET \
 	--env GIT_PROVE_OPTS \
-- 
2.15.0