[Bugfix] Strip target binaries not apply to archive.

Otherwise, we will get some undefined symbols errors.
These errors occur on device testing.

Change-Id: I8af75d1696e629b7afc8788de07c7a4f65de7823
diff --git a/build/tools/build-on-device-toolchain.sh b/build/tools/build-on-device-toolchain.sh
index 08feef9..e3ac336 100755
--- a/build/tools/build-on-device-toolchain.sh
+++ b/build/tools/build-on-device-toolchain.sh
@@ -106,7 +106,7 @@
 
 dump "Strip $ABI binaries"
 STRIP=$NDK_DIR/$(get_default_toolchain_binprefix_for_arch $ARCH)strip
-run find $OUT_SYSROOT/usr/lib \( -name "*\.a" -o -name "*\.so" \) -exec $STRIP --strip-all {} \;
+run find $OUT_SYSROOT/usr/lib \( -name "*\.so" \) -exec $STRIP --strip-all {} \;
 
 dump "Build $ABI LLVM toolchain from $SRC_DIR ..."
 run $BUILDTOOLS/build-device-llvm.sh $FLAGS --abis=$ABI --gcc-version=$GCC_TOOLCHAIN_VERSION $SRC_DIR $NDK_DIR