Allow for ergnomically putting Unix-only files in subdirs by creating INLCUDE_$(pkg) vars

Separate platform-specific files will allow avoiding a lot of CPP.

tests/functional/plugins/local.mk

@@ -8,4 +8,4 @@ libplugintest_ALLOW_UNDEFINED := 1
 
 libplugintest_EXCLUDE_FROM_LIBRARY_LIST := 1
 
-libplugintest_CXXFLAGS := -I src/libutil -I src/libstore -I src/libexpr -I src/libfetchers
+libplugintest_CXXFLAGS := $(INCLUDE_libutil) $(INCLUDE_libstore) $(INCLUDE_libexpr) $(INCLUDE_libfetchers)

tests/functional/test-libstoreconsumer/local.mk

@@ -8,7 +8,7 @@ test-libstoreconsumer_INSTALL_DIR :=
 test-libstoreconsumer_SOURCES := \
   $(wildcard $(d)/*.cc) \
 
-test-libstoreconsumer_CXXFLAGS += -I src/libutil -I src/libstore
+test-libstoreconsumer_CXXFLAGS += $(INCLUDE_libutil) $(INCLUDE_libstore)
 
 test-libstoreconsumer_LIBS = libstore libutil
 

tests/unit/libexpr/local.mk

@@ -23,10 +23,10 @@ libexpr-tests_EXTRA_INCLUDES = \
     -I tests/unit/libexpr-support \
     -I tests/unit/libstore-support \
     -I tests/unit/libutil-support \
-    -I src/libexpr \
-    -I src/libfetchers \
-    -I src/libstore \
-    -I src/libutil
+    $(INCLUDE_libexpr) \
+    $(INCLUDE_libfetchers) \
+    $(INCLUDE_libstore) \
+    $(INCLUDE_libutil)
 
 libexpr-tests_CXXFLAGS += $(libexpr-tests_EXTRA_INCLUDES)
 

tests/unit/libstore/local.mk

@@ -19,8 +19,8 @@ libstore-tests_SOURCES := $(wildcard $(d)/*.cc)
 libstore-tests_EXTRA_INCLUDES = \
     -I tests/unit/libstore-support \
     -I tests/unit/libutil-support \
-    -I src/libstore \
-    -I src/libutil
+    $(INCLUDE_libstore) \
+    $(INCLUDE_libutil)
 
 libstore-tests_CXXFLAGS += $(libstore-tests_EXTRA_INCLUDES)
 

tests/unit/libutil/local.mk

@@ -18,7 +18,7 @@ libutil-tests_SOURCES := $(wildcard $(d)/*.cc)
 
 libutil-tests_EXTRA_INCLUDES = \
     -I tests/unit/libutil-support \
-    -I src/libutil
+    $(INCLUDE_libutil)
 
 libutil-tests_CXXFLAGS += $(libutil-tests_EXTRA_INCLUDES)