Adding option to load ccache in qmake command (build.sh)

build.sh

@@ -231,6 +231,10 @@ while [ "$*" != "" ]; do
     echo "  -libcurl              Use libcurl instead of QtNetwork (for Qt<4.7)"
     echo "  -libexpat             Use libexpat instead of QtXml"
     echo ""
+    echo "Environment Variables:"
+    echo ""
+    echo "  QMAKE_CCACHE=1        Adds CONFIG+=ccache to qmake command (only works if Qt>=5.9.2)"
+    echo ""
     exit 0
     ;;
   *)
@@ -609,6 +613,14 @@ qmake_options=(
   KLAYOUT_VERSION_REV="$KLAYOUT_VERSION_REV"
 )
 
+# This should speed up build time considerably
+# https://ortogonal.github.io/ccache-and-qmake-qtcreator/
+if [ $QMAKE_CCACHE = 1 ]; then
+  qmake_options+=(
+    CONFIG+="ccache"
+  )
+fi
+
 if [ $BUILD_EXPERT = 1 ]; then
   qmake_options+=(
     QMAKE_AR="$AR cqs"

travis-build.sh

@@ -11,6 +11,7 @@ touch build.txt
 # Configure ccache
 mkdir -p ccache;
 export CCACHE_DIR="`pwd`/ccache"
+export QMAKE_CCACHE=1
 
 # Show ccache stats
 echo "Cache stats:"