forkfd/linux: add support for LoongArch
New architecture since 5.15 came out; Qt apps could not create subprocesses without this patch. (In particular, sddm crashes on startup, preventing KDE from working. With the patch applied everything seems OK.)
https://codereview.qt-project.org/c/qt/qtbase/+/440005
This architecture is not CLONE_BACKWARDS in any way.
Matching OpenDCDiag PR: https://github.com/opendcdiag/opendcdiag/pull/169
Pick-to: 6.4 6.2 5.15
Change-Id: Ibceccfd20d270b30302a936885d12e4c55cdd833
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
(cherry picked from commit 0ab51dcc3c0cca0d84822f3871d98ffa46b6b2e4)
Edited by WANG Xuerui