package: involve $CCFLAGS when determing 64-bit arch (re: 9a48ba15)

bin/package, src/cmd/INIT/package.sh:
- It can depend on the compiler flags passed whether the compiler
  produces code for a 64-bit architecture, so pass $CCFLAGS to
  the compiler when testing whether it creates 64-bit object code.

README.md:
- Copy-edit of build instructions.

src/cmd/INIT/package.sh

@@ -2528,7 +2528,7 @@ int b() { return 0; }
 					tmp=hi$$
 					trap 'rm -f $tmp.*' 0 1 2
 					echo 'int main() { return 0; }' > $tmp.a.c
-					$cc -o $tmp.a.exe $tmp.a.c </dev/null >/dev/null 2>&1
+					$cc $CCFLAGS -o $tmp.a.exe $tmp.a.c </dev/null >/dev/null 2>&1
 					file $tmp.a.exe 2>/dev/null | sed "s/$tmp\.a\.exe//g"  `
 				case $bits in
 				*64*)	bits=64 ;;