CI experimental fix

Author: MungoG

build/Jamfile

@@ -69,6 +69,7 @@ lib boost_http_zlib
   : http_zlib_sources
   : requirements
     <library>/boost/http//boost_http
+    <define>BOOST_HTTP_SOURCE
     [ ac.check-library /zlib//zlib : <library>/zlib//zlib : <build>no ]
   : usage-requirements
     <library>/boost/http//boost_http
@@ -84,6 +85,7 @@ lib boost_http_brotli
   : http_brotli_sources
   : requirements
     <library>/boost/http//boost_http
+    <define>BOOST_HTTP_SOURCE
     [ ac.check-library /brotli//brotlicommon : <library>/brotli//brotlicommon : <build>no ]
     [ ac.check-library /brotli//brotlidec : <library>/brotli//brotlidec : <build>no ]
     [ ac.check-library /brotli//brotlienc : <library>/brotli//brotlienc : <build>no ]