[ci] CI fixes (#2161)

* Update setup.sh

* Update test.sh

* Update setup.sh

* test: gcc on Azure

* Update test.sh

* Update setup.sh

* Update test.sh

* switch compiler back on Azure

.ci/setup.sh

@@ -11,6 +11,9 @@ if [[ $OS_NAME == "macos" ]]; then
 #            rm '/usr/local/include/c++'  # previous variant to deal with conflict link
 #            brew cask uninstall oclint  #  reserve variant to deal with conflict link
             brew link --overwrite gcc
+            brew upgrade gcc
+        else
+            brew update
         fi
         if [[ $TASK != "mpi" ]]; then
             brew install gcc

.ci/test.sh

 #!/bin/bash
 
 if [[ $OS_NAME == "macos" ]] && [[ $COMPILER == "gcc" ]]; then
-    export CXX=g++-8
-    export CC=gcc-8
+    export CXX=g++-9
+    export CC=gcc-9
 elif [[ $OS_NAME == "linux" ]] && [[ $COMPILER == "clang" ]]; then
     export CXX=clang++
     export CC=clang