Fixed tests on Windows (including out-of-tree problems)

Modified tcctest.c so that it uses 'double' in place of 'long double'
with MinGW since this is what TCC does, and what Visual C++ does. Added
an option -norunsrc to tcc to allow argv[0] to be set independently of
the compiled source when using tcc -run, which allows tests that rely on
the value of argv[0] to work in out-of-tree builds.

Also added Makefile rules to automatically update out-of-tree build
Makefiles when in-tree Makefiles have changed.

tcc.c

@@ -69,6 +69,7 @@ static void help(void)
            "  -Bdir       use 'dir' as tcc internal library and include path\n"
            "  -MD         generate target dependencies for make\n"
            "  -MF depfile put generated dependencies here\n"
+           "  -norunsrc   Do not compile the file which is the first argument after -run."
            );
 }