travis.yml: Use TRAVIS_BUILD_DIR to refer to the top directory

Travis already has an environment variable that points to the top of
the checked-out source code, TRAVIS_BUILD_DIR. We can use it to avoid
the guessing of the right location of the configure script.

Signed-off-by: Thomas Huth <thuth@redhat.com>
Message-Id: <20200925071147.149406-1-thuth@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/.travis.yml b/.travis.yml
index bd62190..b497264 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -165,8 +165,7 @@
       sudo chmod g+s /usr/bin/qemu-system-* ;
     fi
   - mkdir -p $BUILD_DIR && cd $BUILD_DIR
-  - if [ -e ./configure ]; then ./configure $CONFIG ; fi
-  - if [ -e ../configure ]; then ../configure $CONFIG ; fi
+  - $TRAVIS_BUILD_DIR/configure $CONFIG
 script:
   - make -j3
   - ACCEL="${ACCEL:-tcg}" ./run_tests.sh -v $TESTS | tee results.txt