I'm not quite sure why I put myself through this, but I upgraded my Mac Pro to Mavericks. This broke my local Gitit Wiki. The symptom was that Apache was unable to start, although nothing would be written in the error logs. To determine what was wrong I used sudo apachectl -t. The installer did preserve my http.conf, but wiped out the library mod_proxy_html.so that I had installed in /user/libexec/apache2. See this old entry that I wrote back when I fixed it for Mountain Lion here.
I installed XCode 5 and I thought I was set, but there is more breakage. You might need to run xcode-select --install to get headers in /usr/include. The makefile /usr/share/httpd/build/config_vars.mk is still broken in Mavericks, so commands like sudo apxs -ci -I /usr/include/libxml2 mod_xml2enc.c won't work.
To make a long story short, I got the latest (development) version of the mod_proxy_html source, these commands worked for me:
sudo /usr/share/apr-1/build-1/libtool --silent --mode=compile --tag=CC /usr/bin/cc -DDARW IN -DSIGPROCMASK_SETS_THREAD_MASK -I/usr/local/include -I/usr/include/apache2 -I/usr/include/apr-1 -I/usr/include/libxml2 -I . -c -o mod_xml2enc.lo mod_xml2enc.c && sudo touch mod_xml2enc.slo
and
sudo /usr/share/apr-1/build-1/libtool --silent --mode=compile --tag=CC /usr/bin/cc -DDARW IN -DSIGPROCMASK_SETS_THREAD_MASK -I/usr/local/include -I/usr/include/apache2 -I/usr/include/apr-1 -I/usr/include/libxml2 -I . -c -o mod_proxy_html.lo mod_proxy_html.c && sudo touch mod_proxy_html.slo
Previously, this gave me .so files in the generated .libs directory, but now I just have .o files and I'm not sure that's what I want.