mingw make doesn't conform to the gnu make manual
section 6.9.
according to the manual, make on dos or windows should
use $SHELL for shell if set or otherwise $COMSPEC.
for other platforms the default behaviour is to ignore
$SHELL.
mingw make's behaviour is annoying when you have a
leftover sh.exe somewhere in your path. this is seldom
a problem on unix.
Sincerely Henrik Stokseth.
If this is still an issue then please take it to the make-w32@gnu.org list.