fix(travis): no xrm build failure

install_xcb_xrm.sh takes advantage of the travis cache but it doesn't
actually install the libraries on the system when it finds that the
compilation has been cached.

common/travis/install_xcb_xrm.sh

@@ -1,9 +1,20 @@
 #!/bin/bash
-if [ -z "$(ls -A "${DEPS_DIR}/xcb-util-xrm" 2>/dev/null)" ]; then
+
+# Fail on error
+set -e
+
+# If the Makefile exists, we have already cached xrm
+if [ ! -e "${DEPS_DIR}/xcb-util-xrm/Makefile" ]; then
   git clone --recursive https://github.com/Airblader/xcb-util-xrm
-  cd xcb-util-xrm && {
-    ./autogen.sh --prefix=/usr --libdir=/usr/lib
-    make
-    sudo make install
-  }
 fi
+
+cd xcb-util-xrm
+
+# Install xrm on the system
+# If that doesn't work for some reason (not yet compiled, corrupt cache)
+# we compile xrm and try to install it again
+sudo make install || {
+  ./autogen.sh --prefix=/usr --libdir=/usr/lib
+  make
+  sudo make install
+}