Fix src/ pkg-config API XML paths

The .pc files in src/ are intended for use with the ./run script,
to ease building bindings against an uninstalled libvirt build.
The pointer to the API XML files is incorrect though, it needs to
point into the build tree.

This fixes use of the run script for building libvirt-python, ex:

  /path/to/libvirt.git/run ./setup.py build
Reviewed-by: NDaniel P. Berrangé <berrange@redhat.com>
Signed-off-by: NCole Robinson <crobinso@redhat.com>

src/libvirt-lxc.pc.in

@@ -9,7 +9,7 @@ includedir=@abs_top_builddir@/include
 source_includedir=@abs_top_srcdir@/include
 datarootdir=@abs_top_builddir@
 
-libvirt_lxc_api=@datadir@/docs/libvirt-lxc-api.xml
+libvirt_lxc_api=@abs_top_builddir@/docs/libvirt-lxc-api.xml
 
 Name: libvirt
 Version: @VERSION@

src/libvirt-qemu.pc.in

@@ -9,7 +9,7 @@ includedir=@abs_top_builddir@/include
 source_includedir=@abs_top_srcdir@/include
 datarootdir=@abs_top_builddir@
 
-libvirt_qemu_api=@datadir@/docs/libvirt-qemu-api.xml
+libvirt_qemu_api=@abs_top_builddir@/docs/libvirt-qemu-api.xml
 
 Name: libvirt
 Version: @VERSION@

src/libvirt.pc.in

@@ -9,12 +9,12 @@ includedir=@abs_top_builddir@/include
 source_includedir=@abs_top_srcdir@/include
 datarootdir=@abs_top_builddir@
 
-libvirt_api=@datadir@/docs/libvirt-api.xml
+libvirt_api=@abs_top_builddir@/docs/libvirt-api.xml
 
 # For compat with older versions - also present
 # in libvirt-qemu.pc / libvirt-lxc.pc
-libvirt_qemu_api=@datadir@/docs/libvirt-qemu-api.xml
-libvirt_lxc_api=@datadir@/docs/libvirt-lxc-api.xml
+libvirt_qemu_api=@abs_top_builddir@/docs/libvirt-qemu-api.xml
+libvirt_lxc_api=@abs_top_builddir@/docs/libvirt-lxc-api.xml
 
 Name: libvirt
 Version: @VERSION@