[tools] Fix windows pbc_to_exe, missing unistd.h GH #1114

Thanks to FROGGS for the failure report.
[tools] fixup pbc_to_exe fix, missing unistd.h with --optimize

PARROT_HAS_HEADER_UNISTD is only defined after loading parrot/api.h
Fixes #1117
[tools] more pbc_to_exe fixup for unistd.h with --optimize

Only _WIN32 has no unistd.h. Should close #1117
cygwin: check for wrong gcc-4, --disable-shared

replace wrong gcc-4/g++-4 with gcc/g++. GH #1116
set proper libparrot_ldflags for --disable-shared
  (the static lib is in blib/lib)
fix wrong $disable_shared logic in defaults
[config] silence failing auto::inline probes

Use run_cc_capture and actually check the result. Fixes GH #1118.