Separate openSUSE 16 sccache from the history

Update from:
gcc15-15.2.0+git10201-160000.1.1.x86_64
to
gcc15-15.2.0+git10201-160000.2.1.x86_64
breaks the gcc compability check and causes "false positive"
cache hit which eventually fails with:
"created by a different GCC executable"

Sccache do not seem to see the change as build id, checksums etc.
for the gcc are the same between the versions.

Just set the value to v1 as nothing is pinning the gcc
so it will update on it's own also in future.

Change-Id: I4f2a6da95680c28ad1912751307f96df806c9930
Reviewed-by: Tero Heikkinen <tero.heikkinen@qt.io>
Reviewed-by: Simo Fält <simo.falt@qt.io>

coin/platform_configs/cmake_platforms.yaml

@@ -155,6 +155,7 @@ Configurations:
         'NON_QTBASE_CMAKE_ARGS=-DFFMPEG_DIR={{.Env.FFMPEG_DIR}} -DQT_DEPLOY_FFMPEG=TRUE',
         'VCPKG_HOST_TRIPLET=x64-linux-qt',
         'VCPKG_TARGET_TRIPLET=x64-linux-qt',
+        'SCCACHE_C_CUSTOM_CACHE_BUSTER=v1'
     ]
 -
     Id: 'sles-15_sp6-static'