autogen-native: backport autogen-native POSIX_SHELL fix

fix autogen-native: /bin/sh: bad interpreter: Permission denied
/bin/sh: ../autoopts/tpl/texi2mdoc: /tmp/yocto-autobuilder/yocto-autobuilder/
yocto-worker/res-custom-pyro-multi-: bad interpreter: Permission denied

POSIX_SHELL as shebang doesn't work when it is longer than
BINPRM_BUF_SIZE which is 128 usually. So use "/bin/sh".

Backport: https://bugzilla.yoctoproject.org/show_bug.cgi?id=11965
Backport: https://github.com/RobertBerger/poky/commit/92a17c9074538a38d3d11c063be624f6c62a6352
Bug-AGL: SPEC-892
Change-Id: I12d08e8a89373390b5798ab6ed8d0ff88d0c03c7
Signed-off-by: Matt Ranostay <matt.ranostay@konsulko.com>
Reviewed-on: https://gerrit.automotivelinux.org/gerrit/10931
Tested-by: Jenkins Job builder account <agl-jobbuilder@automotivelinux.org>
ci-image-build: Jenkins Job builder account <agl-jobbuilder@automotivelinux.org>
Reviewed-by: Jan-Simon Moeller <jsmoeller@linuxfoundation.org>