libopenbsd(3): adds pledge(2) and unveil(2) support for Rust; Makefile, include: adds conditional compilation

Makefile

@@ -16,6 +16,9 @@
 DESTDIR ?= dist
 PREFIX ?= /usr/local
 
+# for conditionally compiling OS features
+OS != uname
+
 # normalized prefix
 PREFIX_N != dirname $(PREFIX)/.
 MANDIR != test $(PREFIX_N) = / && printf '/usr/share/man\n' \
@@ -26,8 +29,8 @@ SYSEXITS != printf '\043include <sysexits.h>\n' | cpp -M - | tr ' ' '\n' \
 CC ?= cc
 RUSTC ?= rustc
 RUSTFLAGS += --extern getopt=build/o/libgetopt.rlib \
-	--extern sysexits=build/o/libsysexits.rlib \
-	--extern strerror=build/o/libstrerror.rlib
+	--extern strerror=build/o/libstrerror.rlib \
+	--extern sysexits=build/o/libsysexits.rlib
 CFLAGS += -I$(SYSEXITS)
 
 # testing requires the absolute path to the bin directory set
@@ -74,9 +77,13 @@ docs: docs/ build
 		"s/X\.X\.X/$$(git describe --tags --long | cut -d'-' -f1)/g")"; \
 		sed "s/$$original/$$title/g" <"$$file" >"build/$$file"; done
 
+
+# include OS feature libraries for compilation
+include include/$(OS).mk
+
 .PHONY: rustlibs
-rustlibs: build/o/libsysexits.rlib build/o/libgetopt.rlib \
-	build/o/libstrerror.rlib
+rustlibs: build/o/libgetopt.rlib build/o/libstrerror.rlib \
+	 build/o/libsysexits.rlib $(OSLIB)
 
 build/o/libgetopt.rlib: build src/libgetopt.rs
 	$(RUSTC) $(RUSTFLAGS) --crate-type=lib --crate-name=getopt \