Improve install-build-deps mesa handling.

build/install-build-deps.sh

 #!/bin/bash -e
 
 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # Script to install everything needed to build chromium (well, ideally, anyway)
 # See http://code.google.com/p/chromium/wiki/LinuxBuildInstructions
 # and http://code.google.com/p/chromium/wiki/LinuxBuild64Bit
 
@@ skipping 156 matching lines @@
 nacl_list="g++-mingw-w64-i686 lib32z1-dev
            libasound2:i386 libcap2:i386 libelf-dev:i386 libexif12:i386
            libfontconfig1:i386 libgconf-2-4:i386 libglib2.0-0:i386 libgpm2:i386
            libgtk2.0-0:i386 libncurses5:i386 lib32ncurses5-dev
            libnss3:i386 libpango1.0-0:i386
            libssl1.0.0:i386 libtinfo-dev libtinfo-dev:i386 libtool
            libxcomposite1:i386 libxcursor1:i386 libxdamage1:i386 libxi6:i386
            libxrandr2:i386 libxss1:i386 libxtst6:i386 texinfo xvfb
            ${naclports_list}"
 
-# Find the proper version of libgbm-dev. We can't just install libgbm-dev as
-# it depends on mesa, and only one version of mesa can exists on the system.
-# Hence we must match the same version or this entire script will fail.
-mesa_variant=""
-for variant in "-lts-trusty" "-lts-utopic"; do
-  if $(dpkg-query -Wf'${Status}' libgl1-mesa-glx${variant} 2>/dev/null | \
-       grep -q " ok installed"); then
-    mesa_variant="${variant}"
-  fi
-done
+# Find the proper version of packages that depend on mesa. Only one -lts variant
+# of mesa can be installed and everything that depends on it must match.
+
+# Query for the name and status of all mesa LTS variants, filter for only
+# installed packages, extract just the name, and eliminate duplicates (there can
+# be more than one with the same name in the case of multiarch). Expand into an
+# array.
+mesa_packages=($(dpkg-query -Wf'${package} ${status}\n' \
+                            libgl1-mesa-glx-lts-\* | \
+                 grep " ok installed" | cut -d " " -f 1 | sort -u))
+if [ "${#mesa_packages[@]}" -eq 0 ]; then
+  mesa_variant=""
+elif [ "${#mesa_packages[@]}" -eq 1 ]; then
+  # Strip the base package name and leave just "-lts-whatever"
+  mesa_variant="${mesa_packages[0]#libgl1-mesa-glx}"
+else
+  echo "ERROR: unable to determine which libgl1-mesa-glx variant is installed."
+  exit 1
+fi
 dev_list="${dev_list} libgbm-dev${mesa_variant}
           libgles2-mesa-dev${mesa_variant} libgl1-mesa-dev${mesa_variant}
           mesa-common-dev${mesa_variant}"
 nacl_list="${nacl_list} libgl1-mesa-glx${mesa_variant}:i386"
 
 # Some package names have changed over time
 if package_exists ttf-mscorefonts-installer; then
   dev_list="${dev_list} ttf-mscorefonts-installer"
 else
   dev_list="${dev_list} msttcorefonts"
@@ skipping 256 matching lines @@
   # only contains libcrypto.so.1.0.0 and not the symlink needed for
   # linking (libcrypto.so).
   create_library_symlink /lib/i386-linux-gnu/libcrypto.so.1.0.0 \
       /usr/lib/i386-linux-gnu/libcrypto.so
 
   create_library_symlink /lib/i386-linux-gnu/libssl.so.1.0.0 \
       /usr/lib/i386-linux-gnu/libssl.so
 else
   echo "Skipping symbolic links for NaCl."
 fi