build, test: Fix test logfile name

Co-authored-by: Luke Dashjr <luke-jr+git@utopios.org>

src/Makefile.test.include

@@ -390,14 +390,14 @@ endif
 		grep -E "(BOOST_FIXTURE_TEST_SUITE\\(|BOOST_AUTO_TEST_SUITE\\()" | \
 		cut -d '(' -f 2 | cut -d ',' -f 1 | cut -d ')' -f 1) \
 		from $<
-	$(AM_V_at)$(TEST_BINARY) \
-		--catch_system_errors=no -l test_suite -t "$$(\
+	$(AM_V_at)export TEST_LOGFILE=$(abs_builddir)/$$(\
+	  echo $< | grep -E -o "(wallet/test/.*\.cpp|test/.*\.cpp)" | $(SED) -e s/\.cpp/.log/ \
+	) && \
+	$(TEST_BINARY) --catch_system_errors=no -l test_suite -t "$$(\
 			cat $< | \
 			grep -E "(BOOST_FIXTURE_TEST_SUITE\\(|BOOST_AUTO_TEST_SUITE\\()" | \
 			cut -d '(' -f 2 | cut -d ',' -f 1 | cut -d ')' -f 1\
-		)" -- DEBUG_LOG_OUT > $(abs_builddir)/$$(\
-			echo $< | grep -E -o "(wallet/test/.*\.cpp|test/.*\.cpp)" | $(SED) -e s/\.cpp/.log/\
-		) 2>&1 || (cat $<.log && false)
+	)" -- DEBUG_LOG_OUT > "$$TEST_LOGFILE" 2>&1 || (cat "$$TEST_LOGFILE" && false)
 
 %.json.h: %.json
 	@$(MKDIR_P) $(@D)