Enable optional GCC install and GCC improvements

-By adding MKGCC=yes and MKGCCCMDS=yes on the make commandline
   it is now possible to compile and install GCC on the system.

   Before doing this, if you are not using the build.sh script,
   you will need to call the fetch scripts in order to retrieve
   the sources of GCC and its dependencies.

 -Reduce difference with NetBSD share/mk

   Move Minix-specific parameters from bsd.gcc.mk to bsd.own.mk,
   which is anyway patched, so that bsd.gcc.mk is now aligned
   on the NetBSD version.

 -Clean libraries dependencies, compiles stdc++ only if gcc is
   also compiled (it is part of the gcc sources)

 -Correct minix.h header sequence, cleanup spec headers.

 -Fix cross-compilation from a 32bit host targeting MINIX/arm

Change-Id: I1b234af18eed4ab5675188244e931b2a2b7bd943

test/Makefile

@@ -26,7 +26,6 @@ COPTS.test68.c=	-O0
 
 # Some have special libraries
 LDADD.test59=	-lmthread
-LDFLAGS.mod=	-shared		# make shared object
 
 # Some have an extra file
 OBJS.test57=	test57loop.o
@@ -39,7 +38,7 @@ LDADD.test72+=	-lminixfs
 
 PROGS += testvm
 OBJS.testvm+=	testcache.o
-LDFLAGS.testvm+= -static
+LDSTATIC.testvm= -static
 LDADD.testvm+=	-lsys -ltimers -lminlib
 
 FILES += testvm.conf
@@ -80,7 +79,18 @@ LDSTATIC=	-dynamic
 
 # use the shared linkerscript for mod when using the gold linker
 GOLDLINKERSCRIPT.mod?= ${${HAVE_GOLD:Uno} != "no":? ${LDS_SHARED_LIB} :}
+LDFLAGS.mod+=	-shared		# make shared object
+
+# LSC FIXME: THe bitcode rules need to take into account LDFLAGS
 LDADD.mod+= ${${USE_BITCODE:Uno} != "no":? -shared:}
+
+# Files which have to be compiled with -fPIC
+mod.o: mod.c
+	${COMPILE.c} -fPIC ${.IMPSRC}
+
+common.o: common.c
+	${COMPILE.c} -fPIC ${.IMPSRC}
+
 # test57loop.S is not linked into the .bcl file.
 # This way, we can link it in when linking the final binary
 LDADD.test57+= ${${USE_BITCODE:Uno} != "no":? test57loop.o -Wl,-allow-multiple-definition:}
@@ -88,7 +98,7 @@ LDADD.test57+= ${${USE_BITCODE:Uno} != "no":? test57loop.o -Wl,-allow-multiple-d
 # Add test that must be linked dynamically, and its dynamically loaded
 # module
 PROGS+=		test63 mod
-.endif
+.endif # ${MKPIC} == "yes"
 
 .for o in $(PROGS)
 OBJS.${o} += common.o