package/libgcrypt: fix Thumb mode workaround

Fix the following build failure:

/tmp/ccRqWxnA.s:98: Error: instruction not supported in Thumb16 mode -- `adds ip,fp,r0'

Fixes:
 - http://autobuild.buildroot.org/results/4b96f4e41724e5c9c806a6c7df397a58d1ae1b1e

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Arnout Vandecappelle <arnout@mind.be>

package/libgcrypt/libgcrypt.mk

@@ -27,8 +27,8 @@ LIBGCRYPT_CONF_OPTS += --disable-asm
 endif
 
 # Code doesn't build in thumb mode
-ifeq ($(BR2_arm),y)
-LIBGCRYPT_CONF_ENV += CFLAGS="$(patsubst -mthumb,,$(TARGET_CFLAGS))"
+ifeq ($(BR2_ARM_INSTRUCTIONS_THUMB),y)
+LIBGCRYPT_CONF_ENV += CFLAGS="$(TARGET_CFLAGS) -marm"
 endif
 
 $(eval $(autotools-package))