CI: be sure to exit on failures

[Akim Demaille]

This is very embarrassing.  Because of this stupid mistake, I
have missed several portability failures, and I’ve spent quite
some time this weekend trying to workaround them.

Frustrating.

commit c2e7fc0ea66f4592dbc1fd746863a0fef7ddf1e6
Author: Akim Demaille <address@hidden>
Date:   Sat Sep 15 08:47:10 2018 +0200

    CI: be sure to exit on failures
    
    a807cfa6eb1a5362ead0b7c99bdc8fd2f4f896da completely broke the whole
    point of having a CI: we always exit with success!

diff --git a/.travis.yml b/.travis.yml
index da09fb99..c6ef82af 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -193,8 +193,8 @@ script:
   - git describe || git tag v3.0 -m "Fake version 3.0."
   - git describe
   - ./bootstrap
-  - ./configure --enable-gcc-warnings CC="$CC" CXX="$CXX" || cat config.log
+  - ./configure --enable-gcc-warnings CC="$CC" CXX="$CXX" || { cat config.log 
&& exit 1; }
   - make -j2
-  - make check                     VERBOSE=1 TESTSUITEFLAGS=-j2 || cat 
tests/testsuite.log
-  - make maintainer-check-posix    VERBOSE=1 TESTSUITEFLAGS=-j2 || cat 
tests/testsuite.log
-  - make maintainer-check-g++      VERBOSE=1 TESTSUITEFLAGS=-j2 || cat 
tests/testsuite.log
+  - make check                     VERBOSE=1 TESTSUITEFLAGS=-j2 || { cat 
tests/testsuite.log && exit 1; }
+  - make maintainer-check-posix    VERBOSE=1 TESTSUITEFLAGS=-j2 || { cat 
tests/testsuite.log && exit 1; }
+  - make maintainer-check-g++      VERBOSE=1 TESTSUITEFLAGS=-j2 || { cat 
tests/testsuite.log && exit 1; }