Set openssl PKG_CONFIG_PATH for python 3.7 (#1117)

plugins/python-build/bin/python-build

@@ -1487,6 +1487,7 @@ use_homebrew_openssl() {
   local ssldir="$(brew --prefix openssl 2>/dev/null || true)"
   if [ -d "$ssldir" ]; then
     echo "python-build: use openssl from homebrew"
+    export PKG_CONFIG_PATH="$ssldir/lib/pkgconfig/:${PKG_CONFIG_PATH}"
     export CPPFLAGS="-I$ssldir/include ${CPPFLAGS}"
     export LDFLAGS="-L$ssldir/lib ${LDFLAGS}"
   else