Split Common folder based on operating system families

This change will split common folder to four different folders:
Linux, Unix, Windows and MacOS. Each of these folders includes scripts
which are common for their operating system familes

Task-number: QTQAINFRA-1451
Change-Id: Ic93b2183052335dee875d1452b21e38d268b6474
Reviewed-by: Jędrzej Nowacki <jedrzej.nowacki@qt.io>

coin/provisioning/common/libclang.sh → coin/provisioning/common/unix/libclang.sh

@@ -40,10 +40,10 @@
 # In case of Linux, we expect to get the values as args
 set -e
 
-source "${BASH_SOURCE%/*}/../common/check_and_set_proxy.sh"
+source "${BASH_SOURCE%/*}/check_and_set_proxy.sh"
 
 BASEDIR=$(dirname "$0")
-. $BASEDIR/sw_versions.txt
+. $BASEDIR/../sw_versions.txt
 url=$1
 sha1=$2
 version=$3