Ok but please fix the nit below before commit.

• Add ppc64 fixes

• Drop unnecessary stage0.txt patching

Apply Clang workaround by @tobik to avoid bug reports from outdated llvm90 and facilitate DEFAULT_VERSIONS bump

Ready on amd64 and i386 AFAIC.

• Switch to elfv2 bootstrap built on 12.1-RELEASE with LLVM8

In D24521#539928, @pkubaj wrote:

elfv2 failed with sigsegv:

   Compiling cc v1.0.50
     Running `/wrkdirs/usr/ports/lang/rust/work/rustc-1.43.0-src/build/bootstrap/debug/rustc --crate-name cc --edition=2018 /wrkdirs/usr/ports/lang/rust/work/rustc-1.43.0-src/vendor/cc/src/lib.rs --error-format=json --json=diagnostic-rendered-ansi --crate-type lib --emit=dep-info,metadata,link -C opt-level=3 -C debuginfo=0 -C metadata=4e449c17c9c20698 -C extra-filename=-4e449c17c9c20698 --out-dir /wrkdirs/usr/ports/lang/rust/work/rustc-1.43.0-src/build/powerpc64-unknown-freebsd/stage0-std/release/deps -C linker=gcc9 -L dependency=/wrkdirs/usr/ports/lang/rust/work/rustc-1.43.0-src/build/powerpc64-unknown-freebsd/stage0-std/release/deps --cap-lints allow -Zbinary-dep-depinfo`
rustc command: "LD_LIBRARY_PATH"="/wrkdirs/usr/ports/lang/rust/work/rustc-1.43.0-src/build/powerpc64-unknown-freebsd/stage0/lib:/wrkdirs/usr/ports/lang/rust/work/rustc-1.43.0-src/build/powerpc64-unknown-freebsd/stage0-std/release/deps:/wrkdirs/usr/ports/lang/rust/work/rustc-1.43.0-src/build/powerpc64-unknown-freebsd/stage0/lib" "/wrkdirs/usr/ports/lang/rust/work/rustc-1.43.0-src/build/powerpc64-unknown-freebsd/stage0/bin/rustc" "--crate-name" "cc" "--edition=2018" "/wrkdirs/usr/ports/lang/rust/work/rustc-1.43.0-src/vendor/cc/src/lib.rs" "--error-format=json" "--json=diagnostic-rendered-ansi" "--crate-type" "lib" "--emit=dep-info,metadata,link" "-C" "opt-level=3" "-C" "debuginfo=0" "-C" "metadata=4e449c17c9c20698" "-C"
"extra-filename=-4e449c17c9c20698" "--out-dir" "/wrkdirs/usr/ports/lang/rust/work/rustc-1.43.0-src/build/powerpc64-unknown-freebsd/stage0-std/release/deps" "-C" "linker=gcc9" "-L" "dependency=/wrkdirs/usr/ports/lang/rust/work/rustc-1.43.0-src/build/powerpc64-unknown-freebsd/stage0-std/release/deps" "--cap-lints" "allow" "-Zbinary-dep-depinfo" "-Clinker=gcc9"
sysroot: "/wrkdirs/usr/ports/lang/rust/work/rustc-1.43.0-src/build/powerpc64-unknown-freebsd/stage0-sysroot"
libdir: "/wrkdirs/usr/ports/lang/rust/work/rustc-1.43.0-src/build/powerpc64-unknown-freebsd/stage0/lib"
error: could not compile `cc`.

Caused by:
  process didn't exit successfully: `/wrkdirs/usr/ports/lang/rust/work/rustc-1.43.0-src/build/bootstrap/debug/rustc --crate-name cc --edition=2018 /wrkdirs/usr/ports/lang/rust/work/rustc-1.43.0-src/vendor/cc/src/lib.rs --error-format=json --json=diagnostic-rendered-ansi --crate-type lib --emit=dep-info,metadata,link -C opt-level=3 -C debuginfo=0 -C metadata=4e449c17c9c20698 -C extra-filename=-4e449c17c9c20698 --out-dir /wrkdirs/usr/ports/lang/rust/work/rustc-1.43.0-src/build/powerpc64-unknown-freebsd/stage0-std/release/deps -C linker=gcc9 -L dependency=/wrkdirs/usr/ports/lang/rust/work/rustc-1.43.0-src/build/powerpc64-unknown-freebsd/stage0-std/release/deps --cap-lints allow -Zbinary-dep-depinfo` (signal: 11, SIGSEGV:
invalid memory reference)
command did not execute successfully: "/wrkdirs/usr/ports/lang/rust/work/rustc-1.43.0-src/build/powerpc64-unknown-freebsd/stage0/bin/cargo" "build" "-Zconfig-profile" "--target" "powerpc64-unknown-freebsd" "-Zbinary-dep-depinfo" "-j" "1" "-v" "--release" "--frozen" "--features" "panic-unwind backtrace compiler-builtins-c" "--manifest-path" "/wrkdirs/usr/ports/lang/rust/work/rustc-1.43.0-src/src/libtest/Cargo.toml" "--message-format" "json-render-diagnostics"

In D24521#539743, @mikael wrote:

11.3 i386 : rust ok ; consumers ??
13.0 amd64 : rust ok ; consumers ??
armv7 ok

• Start tracking libgit2 version in BUILD_DEPENDS to prevent bogus bug reports

In D24521#539341, @mikael wrote:

I suppose powerpc will have the same failure as the armv7 but I can't test.

• Add armv7 build fix
• Use aarch64 bootstrap built on 12.1-RELEASE instead (just copied to freefall, so give time to sync or grab from [1])

In D24521#539341, @mikael wrote:

aarch64 is broken:

  extracting cargo-0.43.0-aarch64-unknown-freebsd/cargo/etc/bash_completion.d/cargo
  extracting cargo-0.43.0-aarch64-unknown-freebsd/cargo/bin/cargo
  extracting cargo-0.43.0-aarch64-unknown-freebsd/cargo/share/zsh/site-functions/_cargo
running: /usr/ports/lang/rust/work/rustc-1.43.0-src/build/aarch64-unknown-freebsd/stage0/bin/cargo build --manifest-path /usr/ports/lang/rust/work/rustc-1.43.0-src/src/bootstrap/Cargo.toml --verbose --frozen
error: failed to run `rustc` to learn about target-specific information

Caused by:
  process didn't exit successfully: `/usr/ports/lang/rust/work/rustc-1.43.0-src/build/aarch64-unknown-freebsd/stage0/bin/rustc - --crate-name ___ --print=file-names -Cdebuginfo=2 -C linker=cc -Wrust_2018_idioms -Wunused_lifetimes -Dwarnings --crate-type bin --crate-type rlib --crate-type dylib --crate-type cdylib --crate-type staticlib --crate-type proc-macro --print=sysroot --print=cfg` (exit code: 1)
--- stderr
rustc: Unknown command line argument '-generate-arange-section'.  Try: 'rustc --help'
rustc: Unknown command line argument '-mergefunc-use-aliases'.  Try: 'rustc --help'
rustc: Unknown command line argument '-preserve-alignment-assumptions-during-inlining=false'.  Try: 'rustc --help'

Traceback (most recent call last):
  File "x.py", line 11, in <module>
    bootstrap.main()
  File "/usr/ports/lang/rust/work/rustc-1.43.0-src/src/bootstrap/bootstrap.py", line 950, in main
    bootstrap(help_triggered)
  File "/usr/ports/lang/rust/work/rustc-1.43.0-src/src/bootstrap/bootstrap.py", line 919, in bootstrap
    build.build_bootstrap()
  File "/usr/ports/lang/rust/work/rustc-1.43.0-src/src/bootstrap/bootstrap.py", line 711, in build_bootstrap
    run(args, env=env, verbose=self.verbose)
  File "/usr/ports/lang/rust/work/rustc-1.43.0-src/src/bootstrap/bootstrap.py", line 141, in run
    raise RuntimeError(err)
RuntimeError: failed to run: /usr/ports/lang/rust/work/rustc-1.43.0-src/build/aarch64-unknown-freebsd/stage0/bin/cargo build --manifest-path /usr/ports/lang/rust/work/rustc-1.43.0-src/src/bootstrap/Cargo.toml --verbose --frozen