try to avoid 'by-design' solar-mutex deadlock during ci

Change-Id: I9e1d79613adf6184f76c2e07aca0b78a9329838f
Reviewed-on: https://gerrit.libreoffice.org/25839
Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Norbert Thiebaud <nthiebaud@gmail.com>
diff --git a/solenv/gbuild/platform/windows.mk b/solenv/gbuild/platform/windows.mk
index a2e621d..ebd2a3c 100644
--- a/solenv/gbuild/platform/windows.mk
+++ b/solenv/gbuild/platform/windows.mk
@@ -8,6 +8,9 @@
# file, You can obtain one at http://mozilla.org/MPL/2.0/.
#

# to block heavy exception handling that try to acquire the solarmutex
export LO_LEAN_EXCEPTION=1

# to avoid flashing windows during tests
export VCL_HIDE_WINDOWS=1