Cygwin: Fix testsuite tmpdir creation with non-default cygdrive prefix

winsup/testsuite/Makefile.in

@@ -124,10 +124,11 @@ $(RUNTIME) : $(cygwin_build)/Makefile
 # Set to $(target_alias)/ for cross.
 target_subdir = @target_subdir@
 
-# temporary directory to be used for files created by tests (as an absolute,
-# /cygdrive path, so it can be understood by the test DLL, which will have
-# different mount table)
-tmpdir = $(shell cygpath -ma $(objdir)/testsuite/tmp/ | sed -e 's#^\([A-Z]\):#/cygdrive/\L\1#')
+# a temporary directory, to be used for files created by tests
+tmpdir = $(abspath $(objdir)/testsuite/tmp/)
+# the same temporary directory, as an absolute, /cygdrive path (so it can be
+# understood by the test DLL, which will have a different mount table)
+testdll_tmpdir = $(shell cygpath -ma $(tmpdir) | sed -e 's#^\([A-Z]\):#/cygdrive/\L\1#')
 
 site.exp: ./config.status Makefile
 	@echo "Making a new config file..."
@@ -149,6 +150,7 @@ site.exp: ./config.status Makefile
 	@echo "set CFLAGS \"$(ALL_CFLAGS)\"" >> ./tmp0
 	@echo "set MINGW_CXX \"$(MINGW_CXX)\"" >> ./tmp0
 	@echo "set tmpdir $(tmpdir)" >> ./tmp0
+	@echo "set testdll_tmpdir $(testdll_tmpdir)" >> ./tmp0
 	@echo "set ltp_includes \"$(realpath $(libltp_srcdir))/include\"" >> ./tmp0
 	@echo "## All variables above are generated by configure. Do Not Edit ##" >> ./tmp0
 	@cat ./tmp0 > site.exp

winsup/testsuite/winsup.api/winsup.exp

@@ -69,7 +69,7 @@ foreach src [lsort [glob -nocomplain $srcdir/$subdir/*.c $srcdir/$subdir/*/*.{cc
 	       set redirect_output /dev/null
 	    }
 	    file mkdir $tmpdir/$base
-	    ws_spawn "$rootme/cygrun ./$base.exe $tmpdir/$base > $redirect_output"
+	    ws_spawn "$rootme/cygrun ./$base.exe $testdll_tmpdir/$base > $redirect_output"
 	    file delete -force $tmpdir/$base
 	    if { $rv } {
 		fail "$testcase (execute)"