From: Eric Joldasov <bratishkaerik@getgoogleoff.me>

* Update to use llvm-r1 eclass instead of llvm, zig and
zig-utils eclasses instead of local get_zig_mcpu etc. functions.
* Port "llvm USE-flag" from 9999 ebuild.
* "stage3" compilation is unified by combining build.zig options,
now both cmake (+llvm) and bootstrap.c (-llvm) build up to "zig2"
target, after that we use zig.eclass with common options.
* Before migrating to the zig.eclass, test steps in src_test
have been ran sequentially in for-loop, which allowed logic inside
each step to ran parallelly but not several steps at a time. Now we
use upstream "test" step instead of separately calling all dependant
steps, so that build system can now ran all of them paralelly.
This means time spent in `src_test` is now significantly shorter.
* "zig2" in both scenarios now has explicit target which is set by
using zig-utils.eclass functions on a CBUILD/CHOST. This allows us
to skip convertion logic in CMake and bootstrap.c, so that instead
of patching them we can just update converter in zig-utils.eclass
and unify target behaviour.
* Disable autodocs generation for "std" module, since it can now
be generated on-fly with `zig std` command.

Signed-off-by: Eric Joldasov <bratishkaerik@landless-city.net>
---
....13.0-skip-test-stack_iterator.patch (new) | 32 +++
dev-lang/zig/zig-0.13.0-r2.ebuild (new) | 248 ++++++++++++++++++
2 files changed, 280 insertions(+)

diff --git a/dev-lang/zig/files/zig-0.13.0-skip-test-stack_iterator.patch b/dev-lang/zig/files/zig-0.13.0-skip-test-stack_iterator.patch
new file mode 100644
index 000000000000..e088af2102ed
--- /dev/null
+++ b/dev-lang/zig/files/zig-0.13.0-skip-test-stack_iterator.patch
@@ -0,0 +1,32 @@
+From: Eric Joldasov <bratishkaerik@landless-city.net>
+
+Skip standalone test "stack_iterator" that fail on Gentoo Linux x86_64.
+Fails in ReleaseSafe, ReleaseFast and ReleaseSmall, but not in Debug. +Reported to upstream here https://github.com/ziglang/zig/issues/19944 .
+
+Signed-off-by: Eric Joldasov <bratishkaerik@landless-city.net>
+
+diff --git a/test/standalone/stack_iterator/shared_lib_unwind.zig b/test/standalone/stack_iterator/shared_lib_unwind.zig
+index 57513a49c6..75fddb04c9 100644
+--- a/test/standalone/stack_iterator/share