Makefile: get rid of cmake-build (#2547)

* Makefile: all: only depend on cmake-build

Previously `make` would first run `cmake-build` (`make` in `build/`),
and then run `make -C build awesome` afterwards again (which gets built
by the first step already).

* Makefile: get rid of cmake-build

* Travis: testing previous commits: make distclean

Otherwise it might fail due to permission errors for existing files:

https://travis-ci.org/awesomeWM/awesome/jobs/476612117#L2785

    -- Build files have been written to: /home/travis/build/awesomeWM/awesome/build
    [  1%] Generating manpages/man1/awesome.1
    [  2%] Generating manpages/man1/awesome.1.gz
    /bin/sh: 1: cannot create /home/travis/build/awesomeWM/awesome/build/manpages/man1/awesome.1.gz: Permission denied
    make[3]: *** [manpages/man1/awesome.1.gz] Error 2
    make[2]: *** [CMakeFiles/man.dir/all] Error 2
    make[1]: *** [all] Error 2
    make: *** [cmake-build] Error 2

.travis.yml

@@ -246,6 +246,10 @@ script:
         echo "Testing commit $commit"
         git checkout "$commit"
         git --no-pager show --stat
+
+        # Remove/clean any existing build dir.
+        sudo make distclean
+
         if ! make all check CMAKE_ARGS+="-D DO_COVERAGE=0"; then
           failed="$failed $commit"
         fi

Makefile

@@ -5,12 +5,9 @@ else
     ECHO=@:
 endif
 
-TARGETS=awesome
 BUILDDIR=build
 
-all: $(TARGETS) ;
-
-$(TARGETS): cmake-build
+all: awesome ;
 
 $(BUILDDIR)/Makefile:
 	$(ECHO) "Creating build directory and running cmake in it. You can also run CMake directly, if you want."
@@ -19,10 +16,6 @@ $(BUILDDIR)/Makefile:
 	$(ECHO) "Running cmake…"
 	cd $(BUILDDIR) && cmake $(CMAKE_ARGS) "$(CURDIR)"
 
-cmake-build: $(BUILDDIR)/Makefile
-	$(ECHO) "Building…"
-	$(MAKE) -C $(BUILDDIR)
-
 tags:
 	git ls-files | xargs ctags