build: add LoongArch build infrastructure

[zhaoxiaoqiang007_gmail.com]

Summary

Add sys/conf/{Makefile,files,ldscript,options}.loongarch and wire
loongarch into the top-level Makefiles, bsd.*.mk and the module
build so world and kernels can be built for the architecture.
See the LoongArch kernel commit for architecture references.

Signed-off-by: Xiaoqiang Zhao <[e-mail]>

[shipujin.t_gmail.com]

sys/conf/ldscript.loongarch

74

The missing .init_array/.fini_array is an inconsistency with upstream and may cause constructors not to be executed.
However, modern compilers (GCC/Clang) place generated constructors in .init_array (and .fini_array) by default, not .ctors. If the linker script does not explicitly handle these two sections, they will become orphan sections, which may be discarded or placed in the wrong location, causing global constructors not to be executed.
Add:

.init_array    :   
{
  PROVIDE_HIDDEN (__init_array_start = .); 
  KEEP (*(SORT_BY_INIT_PRIORITY(.init_array.*)))
  KEEP (*(.init_array))
  PROVIDE_HIDDEN (__init_array_end = .); 
}
.fini_array    :   
{
  PROVIDE_HIDDEN (__fini_array_start = .); 
  KEEP (*(SORT_BY_INIT_PRIORITY(.fini_array.*)))
  KEEP (*(.fini_array))
  PROVIDE_HIDDEN (__fini_array_end = .); 
}

93–97

__global_pointer$ is defined here, but it is not referenced anywhere in the LoongArch startup code (locore.S) or under sys/loongarch/, so this definition is currently "dangling" and it is suggested to remove it.

[zhaoxiaoqiang007_gmail.com]

sys/conf/ldscript.loongarch

74

much thanks!

93–97

right

[zhaoxiaoqiang007_gmail.com]

linker scripts fix

[emaste]

share/mk/bsd.cpu.mk

24

should stay in alpha order, so just after i386

share/mk/bsd.endian.mk

10

in alpha order, after i386

[zhaoxiaoqiang007_gmail.com]

share/mk/bsd.cpu.mk

24

Yes, will fix that later

[zhaoxiaoqiang007_gmail.com]

alpha order fix

[imp]

sys/modules/Makefile

672

This list is kinda long, and maybe needs to be the list of things that cxgbe works on.