change pcre2 download url

old ftp.pcre.org is apparently down,
www.pcre.org says to use github as the primary download location

cmake/pcre.cmake

@@ -44,7 +44,7 @@ MACRO(BUNDLE_PCRE2)
   ExternalProject_Add(
     pcre2
     PREFIX   "${dir}"
-    URL      "http://ftp.pcre.org/pub/pcre/pcre2-10.37.zip"
+    URL      "https://github.com/PhilipHazel/pcre2/releases/download/pcre2-10.37/pcre2-10.37.zip"
     URL_MD5  8c1699a725d4b28410adf4b964ebbcb7
     INSTALL_COMMAND ""
     CMAKE_ARGS