"cannot execute [Exec format error]" on cygwin64

[brano-tichy]

ksh93u+ (Version AJM 93u+ 2012-08-01) compiled from source on cygwin64
CYGWIN_NT-10.0 WSHQ1803 3.1.4(0.340/5/3) 2020-02-19 08:49 x86_64 Cygwin
behaves exactly like bug described in RELEASE:

08-12-07 A timing bug on some systems (for example darwin), that could
cause the last process of a pipeline entered interactively to fail
with an "Exec format error" has been fixed.

the error code is 126
setting CCFLAGS=-D_AST_no_spawnveg=1 helped

also lib\libast\path\pathnative.c relies on cygwin_conv_to_win32_path which is not supplied, i had it replaced with cygwin_conv_path