Revive x86_64-linux-android CI with an old nightly

Signed-off-by: Yuki Okushi <jtitor@2k36.org>

.github/workflows/bors.yml

@@ -159,10 +159,7 @@ jobs:
           #wasm32-wasi,
           sparc64-unknown-linux-gnu,
           wasm32-unknown-emscripten,
-          # FIXME: Started to fail since 2022-10-10:
-          # error: linking with `x86_64-linux-android-gcc` failed: exit status: 1
-          # ld: error: cannot find -lunwind
-          # x86_64-linux-android,
+          x86_64-linux-android,
           x86_64-unknown-linux-gnux32,
           x86_64-unknown-linux-musl,
           # FIXME: It seems some items in `src/unix/mod.rs`

ci/install-rust.sh

@@ -8,7 +8,13 @@ toolchain=
 if [ -n "$TOOLCHAIN" ]; then
   toolchain=$TOOLCHAIN
 else
-  toolchain=nightly
+  # Pin the nightly version as newer nightly versions break CI,
+  # https://github.com/rust-lang/rust/issues/103673 contains related information.
+  if [ "$TARGET" = "x86_64-linux-android" ]; then
+    toolchain=nightly-2022-10-09
+  else
+    toolchain=nightly
+  fi
 fi
 if [ "$OS" = "windows" ]; then
   : "${TARGET?The TARGET environment variable must be set.}"