Update GCC version to 9.1.0 in Ubuntu 18.04

Task-number: QTQAINFRA-2958
Change-Id: I3ea8c8e467b9a1f56c2b114c40fb94dfdc1448d0
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Liang Qi <liang.qi@qt.io>

coin/provisioning/common/linux/gcc.sh

@@ -37,6 +37,8 @@
 
 # shellcheck source=../unix/DownloadURL.sh
 source "${BASH_SOURCE%/*}/../unix/DownloadURL.sh"
+# shellcheck source=../unix/SetEnvVar.sh
+source "${BASH_SOURCE%/*}/../unix/SetEnvVar.sh"
 
 set -ex
 
@@ -97,6 +99,9 @@ function InstallGCC() {
         sudo /usr/bin/update-alternatives --install /usr/bin/c++ c++ "$installPrefix/bin/g++-$suffixVersion" "$priority"
     fi
 
+    echo "/usr/local/lib64" | sudo tee /etc/ld.so.conf.d/gcc-libraries.conf
+    echo "/usr/local/lib32" | sudo tee -a /etc/ld.so.conf.d/gcc-libraries.conf
+    sudo ldconfig -v
 
     echo "GCC = $version" >> ~/versions.txt
 }