fix linkage on Xenial (16.04)

[DeckerSU]

This PR fixes linkage error below on Xenial:

/usr/bin/ld: libcc.a(libcc_a-cclib.o): relocation R_X86_64_32 against `.rodata.str1.8' can not be used when making a shared object; recompile with -fPIC
libcc.a: error adding symbols: Bad value
collect2: error: ld returned 1 exit status
Makefile:2305: recipe for target 'komodod' failed
make[2]: *** [komodod] Error 1

[TheComputerGenie]

While I think a PIC flag is a good idea, I cannot help but ask: "Why does anyone care about Xenial?". Xenial support for non-Pro subscribers ended its life some 3 years ago.
Why are we so determined to "lead" the future from as far back as possible?

[DeckerSU]

Why does anyone care about Xenial?

Hmm... the answer is probably "because it costs zero effort," right? If we can support Xenial without any additional resources spent, why not?

[TheComputerGenie]

without any additional resources spent

Given that everything automated is running 20/22, some additional resources are clearly spent going back 2 releases further. At that point, might as well also set it up for Trusty Tahr (since "technically" its full EoL isn't until April 2026), no?

[smk762]

Confirmed successful build via both make and zcutil/build.sh on Ubuntu 16.04