This avoids committing the changes of the 'forceContextQualifier'
properties in the org.eclipse.swt/pom.xml and the binaries/pom.xml after
each change in org.eclipse.swt. Consequently this avoids the noise in
the git-history from these qualifier-change commits and the need to
await the completion of subsequent master-branch builds for consistent
build-qualifiers even for changes that don't change the native binaries.
If not done, this affected the stability of I-builds.

Furthermore this allows further simplifications of the SWT build.

Part of https://github.com/eclipse-platform/eclipse.platform.swt/issues/513