Cache gdb in CI

.travis.yml

@@ -43,6 +43,9 @@ matrix:
 
     - compiler: clang
       env: GCC_VER=5 TARGET=debug CLANG_VER=3.8 PATH=$PWD/llvm-$LLVM_VERSION/bin:$PATH
+      cache:
+        directories:
+          - $GDB_ROOT
 
     - compiler: clang
       env: GCC_VER=5 TARGET=debug.nounity CLANG_VER=3.8 PATH=$PWD/llvm-$LLVM_VERSION/bin:$PATH
@@ -59,6 +62,7 @@ cache:
   - $BOOST_ROOT
   - llvm-$LLVM_VERSION
   - cmake
+  - $GDB_ROOT
 
 before_install:
   - bin/ci/ubuntu/install-dependencies.sh

bin/ci/ubuntu/install-dependencies.sh

@@ -67,9 +67,10 @@ tar xfvz lcov-1.12.tar.gz -C $HOME
 mkdir -p $LCOV_ROOT
 cd $HOME/lcov-1.12 && make install PREFIX=$LCOV_ROOT
 
-if [[ ${TARGET} == debug ]]; then
-    #install gdb
+
+if [[ ${TARGET} == debug && ! -x ${GDB_ROOT}/bin/gdb ]]; then
     pushd $HOME
+    #install gdb
     wget https://ftp.gnu.org/gnu/gdb/gdb-8.0.tar.xz
     tar xf gdb-8.0.tar.xz
     pushd gdb-8.0