mesa: add dependency on libatomic when building for on mips

[flyn-org]

Fix build errors on the noted platforms. Builds were failing with:

Package libmesa-amd is missing dependencies for the following
libraries:
libatomic.so.1

@dangowrt, this seems necessary to fix building on mips, riscv, and x86_64. See also openwrt/packages#26869.

[flyn-org]

The package had used powerpc:libatomic. I think riscv64: will work, since I saw it used in the php8 Makefile. I am not sure if mips, mipsel, and x86_64 are the right names. I did not see this feature documented at https://openwrt.org/docs/guide-developer/dependencies.

[dangowrt]

I see only builds on mips and mipsel platforms currently failing for this reason, but riscv64 and x86_64 builds don't seem to link against libatomic. Can you provide a link to build logs failing on any of those platforms?
On the buildbots x86_64 as well as riscv64 looks all fine, see https://downloads.openwrt.org/snapshots/faillogs/

[flyn-org]

I reduced the change to add the dependency for mips and mipsel only. Some CI strangeness led me to believe riscv and x86_64 require libatmic too, but this is not the case. See openwrt/packages#26814.

[neheb]

That's curious. I wonder if that's the case everywhere.

I know prior versions of GCC needed libatomic under ARM32.