Add our own oniguruma.pc for older distros

Author: nikic

.travis.yml

@@ -86,6 +86,7 @@ install:
 - git pull
 - popd
 - if [[ $RELEASE != precise ]]; then unset ICU_RELEASE; fi # disable ICU installation for Trusty; see https://github.com/travis-ci/travis-ci/issues/3616#issuecomment-286302387
+- export PKG_CONFIG_PATH=$PWD:$PKG_CONFIG_PATH # older distros may not have necessary pkg-config files
 - ./bin/install-icu
 - ./bin/install-libzip
 - ./bin/install-libsodium

oniguruma.pc

@@ -0,0 +1,13 @@
+prefix=/usr
+exec_prefix=/usr
+libdir=/usr/lib/x86_64-linux-gnu
+includedir=/usr/include
+datarootdir=/usr/share
+datadir=/usr/share
+
+Name: oniguruma
+Description: Regular expression library
+Version:
+Requires:
+Libs: -L${libdir} -lonig
+Cflags: -I${includedir}