Don't break file: URLs

solenv/gbuild/platform/WNT_INTEL_MSC.mk

@@ -246,13 +246,19 @@ gb_Helper_set_ld_path := PATH="$${PATH}:$(OUTDIR)/bin"
 # convert parameters filesystem root to native notation
 # does some real work only on windows, make sure not to
 # break the dummy implementations on unx*
+
+# This file:/// -> file:!!! -> file:/// substitution is to protect the
+# slashes after file: in a file: URL from being unduplicated by the
+# // -> / substitution.
 define gb_Helper_convert_native
+$(subst file:!!!,file:///, \
 $(subst //,/, \
+$(subst file:///,file:!!!, \
 $(subst $(REPODIR),$(gb_Helper_REPODIR_NATIVE), \
 $(subst $(SRCDIR),$(gb_Helper_SRCDIR_NATIVE), \
 $(subst $(WORKDIR),$(gb_Helper_WORKDIR_NATIVE), \
 $(subst $(OUTDIR),$(gb_Helper_OUTDIR_NATIVE), \
-$(1))))))
+$(1))))))))
 endef
 
 # YaccTarget class