run-command.h: move declarations for run-command.c from cache.h

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

exec-cmd.c

@@ -1,10 +1,11 @@
-#include "cache.h"
+#include "git-compat-util.h"
 #include "abspath.h"
 #include "environment.h"
 #include "exec-cmd.h"
 #include "gettext.h"
 #include "path.h"
 #include "quote.h"
+#include "run-command.h"
 #include "strvec.h"
 #include "trace.h"
 #include "trace2.h"