build: do not rewrite lua.pc for bootstrapped Lua

scripts/bootstrap-depends.sh

@@ -107,6 +107,7 @@ pkg cmocka ${CMOCKA_URL} ${CMOCKA_TAG} include/cmocka.h
 pkg libuv ${LIBUV_URL} ${LIBUV_TAG} include/uv.h --disable-static
 # lua
 pkg lua ${LUA_URL} ${LUA_TAG} include/lua.h generic install INSTALL_TOP=${PREFIX}
+if [ ! -f ${PREFIX}/lib/pkgconfig/lua.pc ]; then
 cat > ${PREFIX}/lib/pkgconfig/lua.pc << EOF
 prefix=${PREFIX}
 exec_prefix=\${prefix}
@@ -120,6 +121,7 @@ Requires:
 Libs: -L\${libdir} -llua -lm
 Cflags: -I\${includedir}
 EOF
+fi
 
 # remove on successful build
 rm -rf ${BUILD_DIR}