32-bit/64-bit Makefile fix

Counter intuitively, make build ARCH=x86-32 does NOT produce a 32-bit compile
when running a 64-bit OS. Nor would ARCH=x86-64 produce a 64-bit compile when
running a 32-bit OS (assuming it compiled w/o errors).

No functional change

Resolves #621

src/Makefile

@@ -145,7 +145,7 @@ endif
 ifeq ($(COMP),gcc)
 	comp=gcc
 	CXX=g++
-	CXXFLAGS += -pedantic -Wextra -Wshadow
+	CXXFLAGS += -pedantic -Wextra -Wshadow -m$(bits)
 	ifneq ($(UNAME),Darwin)
 	   LDFLAGS += -Wl,--no-as-needed
 	endif
@@ -185,7 +185,8 @@ endif
 ifeq ($(COMP),clang)
 	comp=clang
 	CXX=clang++
-	CXXFLAGS += -pedantic -Wextra -Wshadow
+	CXXFLAGS += -pedantic -Wextra -Wshadow -m$(bits)
+	LDFLAGS += -m$(bits)
 	ifeq ($(UNAME),Darwin)
 		CXXFLAGS += -stdlib=libc++
 		DEPENDFLAGS += -stdlib=libc++