package/libpcap: fix m68k-cf compile issue

Compilation with -Os triggers this assembler problem.
The problematic C code contains a long switch statement, so
everything looks like GCC Bug 104028 is triggered.

Fixes:
 - http://autobuild.buildroot.net/results/db5/db58215fb3c7f30b6c0f0764a84271010346edfb

Signed-off-by: Waldemar Brodkorb <wbx@openadk.org>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/libpcap/libpcap.mk

@@ -57,5 +57,9 @@ ifeq ($(BR2_microblaze)$(BR2_sparc)$(BR2_sparc64),y)
 LIBPCAP_CFLAGS += -fPIC
 endif
 
+ifeq ($(BR2_TOOLCHAIN_HAS_GCC_BUG_104028),y)
+LIBPCAP_CFLAGS += -O2
+endif
+
 $(eval $(autotools-package))
 $(eval $(host-autotools-package))