LIBDIRARCH does not propagate to Makefile

[YaSuenag]

I did not see lib64 under capstone directory when I installed it via make.sh as following:

$ PREFIX=/tmp/capstone ./make.sh install
  :
<snip>
  :
$ ls /tmp/capstone
bin  include  lib

We could not use pkg-config to detect capstone directories because libdir in capstone.pc points to lib64:

$ cat /tmp/capstone/lib/pkgconfig/capstone.pc
Name: capstone
Description: Capstone disassembly engine
Version: 5.0.0
libdir=/tmp/capstone/lib64
includedir=/tmp/capstone/include/capstone
archive=${libdir}/libcapstone.a
Libs: -L${libdir} -lcapstone
Libs.private: -L${libdir} -l:libcapstone.a
Cflags: -I${includedir}
archs=arm aarch64 m68k mips powerpc sparc systemz x86 xcore tms320c64x m680x evm riscv mos65xx wasm bpf sh tricore

make.sh would kick make with LIBDIRARCH=lib64 if /usr/lib64 exists, but it does not propagate to make install. We can see same problem in uninstall(). We need to export or set it to each commands.

[kabeor]

LGTM, thank you for your contribution!