constructs like ${var%$nl}. Apparently this allows the Ubuntu Linux
/bin/sh (dash) to be used as a host shell during the build.
Patch from PR 39786 by Andy Shevchenko.
Build mksyntax directly from mksyntax.c so that the -DTARGET_CHAR=xxx
is applied when it is build.
OTOH mksyntax is broken as it tries to determine properties of the
target system by running code on the build system.