Makefile: fixes test and removes references to the RUSTLIBS variable

Makefile

@@ -18,7 +18,7 @@ PREFIX ?= /usr/local
 
 # normalized prefix
 PREFIX_N != dirname $(PREFIX)/.
-MANDIR != test $(PREFIX_N) -eq / && printf '/usr/share/man\n' \
+MANDIR != test $(PREFIX_N) = / && printf '/usr/share/man\n' \
 	|| printf '/share/man\n'
 SYSEXITS != printf '\043include <sysexits.h>\n' | cpp -M - | tr ' ' '\n' \
 	| sed -n 's/sysexits\.h//p' || printf 'include\n'
@@ -99,22 +99,22 @@ build/bin/false: src/false.c build
 .PHONY: fop
 fop: build/bin/fop
 build/bin/fop: src/fop.rs build rustlibs
-	$(RUSTC) $(RUSTFLAGS) $(RUSTLIBS) -o $@ src/fop.rs
+	$(RUSTC) $(RUSTFLAGS) -o $@ src/fop.rs
 
 .PHONY: hru
 hru: build/bin/hru
 build/bin/hru: src/hru.rs build rustlibs 
-	$(RUSTC) $(RUSTFLAGS) $(RUSTLIBS) -o $@ src/hru.rs
+	$(RUSTC) $(RUSTFLAGS) -o $@ src/hru.rs
 
 .PHONY: intcmp
 intcmp: build/bin/intcmp
 build/bin/intcmp: src/intcmp.rs build rustlibs
-	$(RUSTC) $(RUSTFLAGS) $(RUSTLIBS) -o $@ src/intcmp.rs
+	$(RUSTC) $(RUSTFLAGS) -o $@ src/intcmp.rs
 
 .PHONY: mm
 mm: build/bin/mm
 build/bin/mm: src/mm.rs build rustlibs 
-	$(RUSTC) $(RUSTFLAGS) $(RUSTLIBS) -o $@ src/mm.rs
+	$(RUSTC) $(RUSTFLAGS) -o $@ src/mm.rs
 
 .PHONY: npc
 npc: build/bin/npc
@@ -124,7 +124,7 @@ build/bin/npc: src/npc.c build
 .PHONY: rpn
 rpn: build/bin/rpn
 build/bin/rpn: src/rpn.rs build rustlibs
-	$(RUSTC) $(RUSTFLAGS) $(RUSTLIBS) -o $@ src/rpn.rs
+	$(RUSTC) $(RUSTFLAGS) -o $@ src/rpn.rs
 
 .PHONY: scrut
 scrut: build/bin/scrut
@@ -144,7 +144,7 @@ build/bin/strcmp: src/strcmp.c build
 .PHONY: swab
 swab: build/bin/swab
 build/bin/swab: src/swab.rs build rustlibs
-	$(RUSTC) $(RUSTFLAGS) $(RUSTLIBS) -o $@ src/swab.rs
+	$(RUSTC) $(RUSTFLAGS) -o $@ src/swab.rs
 
 .PHONY: true
 true: build/bin/true