Add our own libjpeg.pc if it doesn't exist yet

Author: nikic

.travis.yml

@@ -86,6 +86,10 @@ install:
 - git pull
 - popd
 - if [[ $RELEASE != precise ]]; then unset ICU_RELEASE; fi # disable ICU installation for Trusty; see https://github.com/travis-ci/travis-ci/issues/3616#issuecomment-286302387
+- | # older distros don't ship a libjpeg.pc, add our own to pkg-config path
+  if ! pkg-config --exists libjpeg; then
+    export PKG_CONFIG_PATH=$PWD:$PKG_CONFIG_PATH
+  fi
 - ./bin/install-icu
 - ./bin/install-libzip
 - ./bin/install-libsodium

libjpeg.pc

@@ -0,0 +1,10 @@
+prefix=/usr
+exec_prefix=${prefix}
+libdir=${prefix}/lib/x86_64-linux-gnu
+includedir=${prefix}/include
+
+Name: libjpeg
+Description: JPEG image codec
+Version: 
+Libs: -L${libdir} -ljpeg
+Cflags: -I${includedir}