Speed up static archive stripping processing (#517101)

- only bother processing files named *.a instead of everything in buildroot
- patch from Adam Jackson

brp-strip-static-archive

@@ -8,7 +8,7 @@ fi
 [ -z "$STRIP" ] && STRIP=strip
 
 # Strip static libraries.
-for f in `find $RPM_BUILD_ROOT -type f -a -exec file {} \; | \
+for f in `find $RPM_BUILD_ROOT -name \*.a -a -exec file {} \; | \
         grep -v "^${RPM_BUILD_ROOT}/\?usr/lib/debug"  | \
 	grep 'current ar archive' | \
 	sed -n -e 's/^\(.*\):[ 	]*current ar archive/\1/p'`; do