Added configurable `INCLUDE_PREFIX` for install targets.

Fortune for memfd_secret-shim's current commit: Future curse − 末凶

Makefile

@@ -26,6 +26,8 @@ ifeq ($(PREFIX),)
 	PREFIX := /usr/local
 endif
 
+INCLUDE_PREFIX := $(PROJECT)/
+
 # Default archivers
 AR?=ar
 RANLIB?=ranlib
@@ -343,12 +345,13 @@ install:
 	install -s -m 755 lib$(PROJECT).so.$(VERSION) $(DESTDIR)$(PREFIX)/lib/
 	ln -sf lib$(PROJECT).so.$(VERSION) $(DESTDIR)$(PREFIX)/lib/lib$(PROJECT).so.$(VERSION_MAJOR)
 	ln -sf lib$(PROJECT).so.$(VERSION_MAJOR) $(DESTDIR)$(PREFIX)/lib/lib$(PROJECT).so
-	install -d $(DESTDIR)$(PREFIX)/include/$(PROJECT)/
-	install -m 644 $(wildcard $(INCLUDE)/*.*) $(DESTDIR)$(PREFIX)/include/$(PROJECT)/
+	install -d $(DESTDIR)$(PREFIX)/include/$(INCLUDE_PREFIX)
+	install -m 644 $(wildcard $(INCLUDE)/*.*) $(DESTDIR)$(PREFIX)/include/$(INCLUDE_PREFIX)
 uninstall:
 	-rm $(DESTDIR)$(PREFIX)/lib/lib$(PROJECT).{a,so{,.*}}
-	cd $(INCLUDE) && find . -type f | xargs -I {} rm "$(DESTDIR)$(PREFIX)/include/$(PROJECT)/{}"
-	rmdir $(DESTDIR)$(PREFIX)/include/$(PROJECT)
+	cd $(INCLUDE) && find . -type f | xargs -I {} rm "$(DESTDIR)$(PREFIX)/include/$(INCLUDE_PREFIX){}"
+	[[ -d "$(DESTDIR)$(PREFIX)/include/$(INCLUDE_PREFIX)" ]] && \
+		rmdir $(DESTDIR)$(PREFIX)/include/$(INCLUDE_PREFIX) || :
 
 #TODO: We can make the target between `{debug,release}{.a,.so}` configurable by call. e.g. `TARGET=release.a make test`
 $(PROJECT)-test: LDFLAGS+= -lfmt -lstdc++