diffstat: fix wrong evaluation of CC

diffstat checks variable CC. If options '-I', '-U' or '-D' is included
in CC, variable CC will be wrongly filtered and only such as
'mips64-wrsmllibn32-linux-gnun32-gcc' left. It shows warning message
during configure:

| checking $CC variable...broken
| configure: WARNING: your environment misuses the CC variable to hold CFLAGS/CPPFLAGS options

Disable such check for OE.

(From OE-Core rev: c330036e1e6151246b736f88f7412e9e4ac38d5f)

Signed-off-by: Kai Kang <kai.kang@windriver.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-devtools/diffstat/diffstat/avoid-check-user-break-cc.patch

@@ -0,0 +1,26 @@
+Upstream-Status: Inappropriate [oe specific]
+
+m4 function CF_CC_ENV_FLAGS checks whether variable CC contains options '-I', '-U'
+and '-D'. It is not suitable for oe that option such as '-D_FORTIFY_SOURCE=2' may
+be included in CC. And then CC will be wrongly filtered.
+
+So comment out CF_CC_ENV_FLAGS from function CF_PROG_CC.
+
+Signed-off-by: Kai Kang <kai.kang@windriver.com>
+---
+ aclocal.m4 | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/aclocal.m4 b/aclocal.m4
+index 420fe83..eb73ea9 100644
+--- a/aclocal.m4
++++ b/aclocal.m4
+@@ -1114,7 +1114,7 @@ CF_GCC_VERSION
+ CF_ACVERSION_CHECK(2.52,
+ 	[AC_PROG_CC_STDC],
+ 	[CF_ANSI_CC_REQD])
+-CF_CC_ENV_FLAGS
++dnl CF_CC_ENV_FLAGS
+ ])dnl
+ dnl ---------------------------------------------------------------------------
+ dnl CF_PROG_GROFF version: 2 updated: 2015/07/04 11:16:27