Include win directory in pigz even if not using threads.

[nmoinvaz]

This PR always includes win directory in pigz when on Windows even if not using pthreads. This win directory contains source code the mimic the necessary linux functions. https://github.com/zlib-ng/pigzbench/tree/master/pigz/win
By not compiling with pthreads on Windows we can get to compiling pigz quicker for testing functional issues unrelated to threading.

[codecov]

Codecov Report

Merging #1035 (73c58bd) into develop (e128537) will decrease coverage by 0.01%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           develop    #1035      +/-   ##
===========================================
- Coverage    78.32%   78.31%   -0.02%     
===========================================
  Files           85       85              
  Lines         8730     8730              
  Branches      1392     1392              
===========================================
- Hits          6838     6837       -1     
  Misses        1357     1357              
- Partials       535      536       +1     

Flag	Coverage Δ
macos_clang	68.06% <ø> (ø)
macos_gcc	66.70% <ø> (ø)
ubuntu_clang	73.36% <ø> (ø)
ubuntu_clang_debug	73.68% <ø> (ø)
ubuntu_clang_inflate_allow_invalid_dist	73.11% <ø> (ø)
ubuntu_clang_inflate_strict	73.35% <ø> (ø)
ubuntu_clang_mmap	73.34% <ø> (ø)
ubuntu_clang_msan	73.36% <ø> (ø)
ubuntu_clang_pigz	34.08% <ø> (ø)
ubuntu_clang_pigz_no_optim	38.18% <ø> (ø)
ubuntu_clang_pigz_no_threads	33.62% <ø> (ø)
ubuntu_clang_reduced_mem	73.63% <ø> (ø)
ubuntu_gcc	72.83% <ø> (ø)
ubuntu_gcc_aarch64	74.74% <ø> (ø)
ubuntu_gcc_aarch64_compat_no_opt	72.38% <ø> (ø)
ubuntu_gcc_aarch64_no_acle	74.02% <ø> (ø)
ubuntu_gcc_aarch64_no_neon	74.29% <ø> (ø)
ubuntu_gcc_armhf	74.73% <ø> (ø)
ubuntu_gcc_armhf_compat_no_opt	72.35% <ø> (ø)
ubuntu_gcc_armhf_no_acle	74.99% <ø> (ø)
ubuntu_gcc_armhf_no_neon	75.23% <ø> (ø)
ubuntu_gcc_armsf	74.74% <ø> (ø)
ubuntu_gcc_armsf_compat_no_opt	72.35% <ø> (ø)
ubuntu_gcc_compat_no_opt	73.49% <ø> (ø)
ubuntu_gcc_mingw_i686	0.00% <ø> (ø)
ubuntu_gcc_mingw_x86_64	0.00% <ø> (ø)
ubuntu_gcc_no_avx2	74.71% <ø> (ø)
ubuntu_gcc_no_pclmulqdq	71.40% <ø> (ø)
ubuntu_gcc_no_sse2	73.81% <ø> (ø)
ubuntu_gcc_no_sse4	71.72% <ø> (ø)
ubuntu_gcc_o3	72.03% <ø> (ø)
ubuntu_gcc_osb	75.85% <ø> (ø)
ubuntu_gcc_pigz	34.43% <ø> (ø)
ubuntu_gcc_pigz_aarch64	36.15% <ø> (+0.03%)	⬆️
ubuntu_gcc_ppc	72.71% <ø> (ø)
ubuntu_gcc_ppc64	75.61% <ø> (ø)
ubuntu_gcc_ppc64le	74.15% <ø> (ø)
ubuntu_gcc_ppc_no_power8	75.25% <ø> (ø)
ubuntu_gcc_s390x	74.05% <ø> (ø)
ubuntu_gcc_sparc64	76.39% <ø> (ø)
win64_gcc	∅ <ø> (∅)
win64_gcc_compat_no_opt	∅ <ø> (∅)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
trees.c	96.17% <0.00%> (-0.28%)	⬇️

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[Dead2]

LGTM