btrfs-progs: ci: enable musl build tests in docker

Enable docker in travis and start build test(s) before our testsuite.
Now for musl libc, so we don't accidentally break the build anymore.

Issue: #29
Signed-off-by: David Sterba <dsterba@suse.com>

.travis.yml

@@ -39,6 +39,9 @@ branches:
   - master
   - release-test
 
+services:
+  - docker
+
 env:
   global:
    # The next declaration is the encrypted COVERITY_SCAN_TOKEN, created
@@ -49,6 +52,7 @@ before_install:
   - sudo apt-get update -qq
   - sudo apt-get install -qq e2fslibs-dev gcc libacl1-dev libblkid-dev liblzo2-dev make pkg-config udev zlib1g-dev acl attr reiserfsprogs
   - echo -n | openssl s_client -connect scan.coverity.com:443 | sed -ne '/-BEGIN CERTIFICATE-/,/-END CERTIFICATE-/p' | sudo tee -a /etc/ssl/certs/ca-
+  - docker pull kdave/ci-musl-x86_64
   - "mkdir tmp-reiser;
      cd tmp-reiser;
      wget https://www.kernel.org/pub/linux/kernel/people/jeffm/reiserfsprogs/v3.6.27/reiserfsprogs-3.6.27.tar.xz;
@@ -81,9 +85,13 @@ addons:
     branch_pattern: coverity_scan
 
 script:
+  # quick build tests
+  - "if travis/should-run-test; then docker run -it kdave/ci-musl-x86_64 ./test-build $TRAVIS_BRANCH --disable-documentation --disable-backtrace; fi"
+  # real tests
   - "if travis/should-run-test; then make TEST_LOG=dump test-cli; fi"
   - "if travis/should-run-test; then make TEST_LOG=dump test-mkfs; fi"
   - "if travis/should-run-test; then make TEST_LOG=dump test-check; fi"
   - "if travis/should-run-test; then make TEST_LOG=dump TEST_ENABLE_OVERRIDE=true TEST_ARGS_CHECK=--mode=lowmem test-check; fi"
   - "if travis/should-run-test; then make TEST_LOG=dump test-misc; fi"
+  # long running tests
   - "if [ $TRAVIS_BRANCH = release-test ]; then make TEST_LOG=dump test-convert; fi"