For Travis CI - use Release build configuration when build on bad VM.

Now this rule is applicable for all target platforms (Linux, Windows, Android, and Raspberry-Pi) which have their CI builds run on Linux/Ubuntu host VM. Mac OSX and iOS CI builds are not affected by this rule since they run on OSX host VM which is not susceptible to "bad VM" issue. The idea is to reduce memory consumption during the linking phase and thus avoiding the process being killed due to insufficient memory in the VM.

.travis.yml

@@ -54,6 +54,7 @@ matrix:
       env: LINUX=1 URHO3D_LIB_TYPE=SHARED URHO3D_64BIT=0
 before_install:
   - free -tm
+  - mem=($(free -m |head -2 |tail -1)); if [ ${mem[6]} -eq 0 ]; then export BAD_VM=1; fi
   - export TAG=$(git describe --exact-match $TRAVIS_COMMIT 2>/dev/null); if [[ $TAG =~ [[:digit:]]+\.[[:digit:]]+ ]]; then export RELEASE_TAG=$TAG; fi
   - if [ $RELEASE_TAG ] || ([ "$TRAVIS_BRANCH" == "master" ] && [ "$TRAVIS_PULL_REQUEST" == "false" ]); then export SITE_UPDATE_ON_MASTER_COMMIT=$SITE_UPDATE; export COMMIT_MESSAGE=$(git log --format=%B -n 1 $TRAVIS_COMMIT); if [ "$CC" == "gcc" ] && ([ $RELEASE_TAG ] || echo $COMMIT_MESSAGE |grep -cq '\[ci package\]'); then export PACKAGE_UPLOAD=1; fi; fi
   - if [ "$SITE_UPDATE_ON_MASTER_COMMIT" -o "$PACKAGE_UPLOAD" ]; then travis_retry sudo add-apt-repository ppa:george-edison55/precise-backports -y; fi

Rakefile

@@ -76,8 +76,8 @@ task :ci do
   if ENV['CI'] && ENV['PACKAGE_UPLOAD'] && !ENV['RELEASE_TAG']
     system 'git fetch --unshallow' or abort 'Failed to unshallow cloned repository'
   end
-  # Packaging always use Release configuration (temporary workaround due to Travis-CI insufficient memory, also always use Release configuration for MinGW and Android build)
-  if ENV['PACKAGE_UPLOAD'] || (ENV['CI'] && (ENV['WINDOWS'] || ENV['ANDROID']))
+  # Packaging always use Release configuration (temporary workaround due to Travis-CI insufficient memory, also use Release configuration when CI build runs on a bad VM)
+  if ENV['PACKAGE_UPLOAD'] || ENV['BAD_VM']
     $configuration = 'Release'
     $testing = 0
   else