[ccache] permit ccache to build with clang

[Joel Rosdahl]

On 18 September 2012 18:21, Eitan Adler <lists at eitanadler.com> wrote:
> I needed the following patch for ccache to build with clang.
> [...]
> -all_cppflags = @DEFS@ @extra_cppflags@ -DSYSCONFDIR=$(sysconfdir) -I.
> -I$(srcdir) $(CPPFLAGS)

(Your patch doesn't apply since it's garbled. The above two lines
should be one.)

> +all_cppflags = @DEFS@ @extra_cppflags@ -DSYSCONFDIR=$(sysconfdir) $(CPPFLAGS)

This breaks out-of-source builds:

    % mkdir build
    % cd build
    % ../configure CC=clang
    % make test
    [...]
    clang -DHAVE_CONFIG_H  -DSYSCONFDIR=/usr/local/etc  -MD -MP -MF
.deps/test_main.c.d -g -O2 -Wall -W -Werror -c -o test/main.o
../test/main.c
    ../test/main.c:20:10: fatal error: 'test/framework.h' file not found
    #include "test/framework.h"
             ^
    1 error generated.
    make: *** [test/main.o] Error 1

So, I can't apply it. I think it's quite silly of clang to warn about
unused -I options; it would be a hassle to add -I options potentially
tailored for each source code file.

-- Joel