nxagent: implement RPATH/RUNPATH override for libX11.

As discussed in ArcticaProject/nx-libs#610, we need a way to load
libNX_X11 as a fake version of libX11 into nxagent's address space.

For doing so, we have to link against libX11 at build-time and specify
a(n) RPATH/RUNPATH to our libX11 -> libNX_X11 compat symlinks.

This commit is essentially doing a cross between options 3 and 4
discussed in the provided GH issue.

We link libX11 early (before specifying -Lcompat_symlinks_dir), so that
the linker finds the "real" libX11 version with the libX11 SONAME. This
leads to our binary depending upon both libX11 and libNX_X11 SONAMEs. We
already always added RPATH/RUNPATH, but these values are not passed down
to dependent libraries.

What happens at run-time is that the loader searches for a libX11
SONAME, takes RPATH/RUNPATH into account and loads our libNX_X11 library
instead via the compat symlinks. This satisfies the libX11 SONAME and
dependent libraries will *not* load the system libX11 version again.

Debian's dpkg-shlibdeps isn't quite happy about this mismatching SONAME
situation, so instruct to look the other way while we're minding our
business.

Fixes: ArcticaProject/nx-libs#610

1 files changed, 8 insertions, 0 deletions

diff --git a/debian/rules b/debian/rules
index 90234c516..b2258cd58 100755
--- a/debian/rules
+++ b/debian/rules
@@ -124,5 +124,13 @@ override_dh_strip:
 override_dh_makeshlibs:
 	dh_makeshlibs -n
 
+# Needed for the libX11 RUNPATH/RPATH link-time hack.
+# dh_shlibdeps will follow dependencies within binaries and choke
+# on the libX11 dependency, since the SONAME (libX11.*) used while linking
+# does not match the later detected SONAME (libNX_X11.*) obtained through
+# the libX11 -> libNX_X11 compat symlink.
+override_dh_shlibdeps:
+	dh_shlibdeps --dpkg-shlibdeps-params=--ignore-missing-info
+
 get-orig-source:
 	uscan --noconf --force-download --rename --download-current-version --destdir=..