Use an out-of-tree build for one Travis job

Signed-off-by: Uli Schlachter <psychon@znc.in>

.travis.yml

@@ -5,7 +5,7 @@ env:
   matrix:
     - LUA=5.2 LUANAME=lua5.2 BUILD_APIDOC=true DO_COVERAGE=true
     # Note: luarocks does not work with Lua 5.0.
-    - LUA=5.1 LUANAME=lua5.1
+    - LUA=5.1 LUANAME=lua5.1 BUILD_IN_DIR=/tmp/awesome-build
     # luajit: installed from source.
     - LUA=5.1 LUANAME=luajit-2.0 LUALIBRARY=/usr/lib/libluajit-5.1.so LUAROCKS_ARGS=--lua-suffix=jit-2.0.4
     - LUA=5.2 LUANAME=lua5.2 LGIVER=0.7.1
@@ -91,6 +91,13 @@ install:
 
 script:
   - export CMAKE_ARGS="-DLUA_LIBRARY=${LUALIBRARY} -DLUA_INCLUDE_DIR=${LUAINCLUDE} -D OVERRIDE_VERSION=$AWESOME_VERSION"
+  - |
+    if [ -n "$BUILD_IN_DIR" ]; then
+        SOURCE_DIRECTORY="$PWD"
+        mkdir "$BUILD_IN_DIR"
+        cd "$BUILD_IN_DIR"
+        cmake $CMAKE_ARGS "$SOURCE_DIRECTORY"
+    fi
   - make && sudo env PATH=$PATH make install && awesome --version && make check
   - |
     if [ "$DO_COVERAGE" = "true" ]; then