Fix Windows path separator

...broken since 84ef6d82546b044990f4efd57e51e29c6c6565c8 "Build external lxml if
not provided by system"

Change-Id: Ie76c32a1d3094e6d98db7d50195571ae31c0ada6
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/161536
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <stephan.bergmann@allotropia.de>
(cherry picked from commit 661f06a3c7f1a395d38981958e5ea72a85040a30)
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/161554
diff --git a/solenv/gbuild/platform/com_MSC_class.mk b/solenv/gbuild/platform/com_MSC_class.mk
index d8cab84..16cc420 100644
--- a/solenv/gbuild/platform/com_MSC_class.mk
+++ b/solenv/gbuild/platform/com_MSC_class.mk
@@ -740,7 +740,7 @@ gb_UIMenubarTarget_UIMenubarTarget_platform :=

# Python
gb_Python_HOME := $(INSTDIR_FOR_BUILD)/program/python-core-$(PYTHON_VERSION)
gb_Python_PRECOMMAND := PATH="$(shell cygpath -w $(INSTDIR_FOR_BUILD)/program)" PYTHONHOME="$(gb_Python_HOME)" PYTHONPATH="$${PYPATH:+$$PYPATH:}$(gb_Python_HOME)/lib;$(gb_Python_HOME)/lib/lib-dynload:$(INSTDIR_FOR_BUILD)/program"
gb_Python_PRECOMMAND := PATH="$(shell cygpath -w $(INSTDIR_FOR_BUILD)/program)" PYTHONHOME="$(gb_Python_HOME)" PYTHONPATH="$${PYPATH:+$$PYPATH;}$(gb_Python_HOME)/lib;$(gb_Python_HOME)/lib/lib-dynload:$(INSTDIR_FOR_BUILD)/program"
gb_Python_INSTALLED_EXECUTABLE := $(INSTROOT_FOR_BUILD)/$(LIBO_BIN_FOLDER)/python.exe

gb_ICU_PRECOMMAND := PATH="$(shell cygpath -w $(WORKDIR_FOR_BUILD)/UnpackedTarball/icu/source/lib)"