Put unit tests back in old build system for now

tests/unit/libexpr/local.mk

@@ -0,0 +1,45 @@
+check: libexpr-tests_RUN
+
+programs += libexpr-tests
+
+libexpr-tests_NAME := libnixexpr-tests
+
+libexpr-tests_ENV := _NIX_TEST_UNIT_DATA=$(d)/data GTEST_OUTPUT=xml:$$testresults/libexpr-tests.xml
+
+libexpr-tests_DIR := $(d)
+
+ifeq ($(INSTALL_UNIT_TESTS), yes)
+  libexpr-tests_INSTALL_DIR := $(checkbindir)
+else
+  libexpr-tests_INSTALL_DIR :=
+endif
+
+libexpr-tests_SOURCES := \
+    $(wildcard $(d)/*.cc) \
+    $(wildcard $(d)/value/*.cc) \
+    $(wildcard $(d)/flake/*.cc)
+
+libexpr-tests_EXTRA_INCLUDES = \
+    -I tests/unit/libexpr-support \
+    -I tests/unit/libstore-support \
+    -I tests/unit/libutil-support \
+    $(INCLUDE_libexpr) \
+    $(INCLUDE_libexprc) \
+    $(INCLUDE_libfetchers) \
+    $(INCLUDE_libstore) \
+    $(INCLUDE_libstorec) \
+    $(INCLUDE_libutil) \
+    $(INCLUDE_libutilc)
+
+libexpr-tests_CXXFLAGS += $(libexpr-tests_EXTRA_INCLUDES)
+
+libexpr-tests_LIBS = \
+    libexpr-test-support libstore-test-support libutil-test-support \
+    libexpr libexprc libfetchers libstore libstorec libutil libutilc
+
+libexpr-tests_LDFLAGS := -lrapidcheck $(GTEST_LIBS) -lgmock
+
+ifdef HOST_WINDOWS
+  # Increase the default reserved stack size to 65 MB so Nix doesn't run out of space
+  libexpr-tests_LDFLAGS += -Wl,--stack,$(shell echo $$((65 * 1024 * 1024)))
+endif