ci: Temporarily disable 32-bit sparc build

```
2024-09-04T16:45:12.2014179Z #28 16.61   = note: /usr/lib/gcc-cross/sparc64-linux-gnu/7/../../../../sparc64-linux-gnu/bin/ld: /tmp/test-gcc/rust/target/sparc-unknown-linux-gnu/debug/deps/rust_test-f42554a7f87dbfdd.0j8wch5gx7yj5jefbnbiu2it7.rcgu.o: Relocations in generic ELF (EM: 18)
2024-09-04T16:45:12.2017197Z #28 16.61           /usr/lib/gcc-cross/sparc64-linux-gnu/7/../../../../sparc64-linux-gnu/bin/ld: /tmp/test-gcc/rust/target/sparc-unknown-linux-gnu/debug/deps/rust_test-f42554a7f87dbfdd.0j8wch5gx7yj5jefbnbiu2it7.rcgu.o: Relocations in generic ELF (EM: 18)
2024-09-04T16:45:12.2020076Z #28 16.61           /usr/lib/gcc-cross/sparc64-linux-gnu/7/../../../../sparc64-linux-gnu/bin/ld: /tmp/test-gcc/rust/target/sparc-unknown-linux-gnu/debug/deps/rust_test-f42554a7f87dbfdd.0j8wch5gx7yj5jefbnbiu2it7.rcgu.o: Relocations in generic ELF (EM: 18)
2024-09-04T16:45:12.2023137Z #28 16.61           /usr/lib/gcc-cross/sparc64-linux-gnu/7/../../../../sparc64-linux-gnu/bin/ld: /tmp/test-gcc/rust/target/sparc-unknown-linux-gnu/debug/deps/rust_test-f42554a7f87dbfdd.0j8wch5gx7yj5jefbnbiu2it7.rcgu.o: Relocations in generic ELF (EM: 18)
2024-09-04T16:45:12.2025832Z #28 16.61           /usr/lib/gcc-cross/sparc64-linux-gnu/7/../../../../sparc64-linux-gnu/bin/ld: /tmp/test-gcc/rust/target/sparc-unknown-linux-gnu/debug/deps/rust_test-f42554a7f87dbfdd.0j8wch5gx7yj5jefbnbiu2it7.rcgu.o: Relocations in generic ELF (EM: 18)
2024-09-04T16:45:12.2029640Z #28 16.61           /usr/lib/gcc-cross/sparc64-linux-gnu/7/../../../../sparc64-linux-gnu/bin/ld: /tmp/test-gcc/rust/target/sparc-unknown-linux-gnu/debug/deps/rust_test-f42554a7f87dbfdd.0j8wch5gx7yj5jefbnbiu2it7.rcgu.o: Relocations in generic ELF (EM: 18)
2024-09-04T16:45:12.2032171Z #28 16.61           /tmp/test-gcc/rust/target/sparc-unknown-linux-gnu/debug/deps/rust_test-f42554a7f87dbfdd.0j8wch5gx7yj5jefbnbiu2it7.rcgu.o: error adding symbols: File in wrong format
2024-09-04T16:45:12.2033630Z #28 16.61           collect2: error: ld returned 1 exit status
2024-09-04T16:45:12.2034203Z #28 16.61
2024-09-04T16:45:12.2034439Z #28 16.61
2024-09-04T16:45:12.2035038Z #28 16.63 error: could not compile `rust-test` (bin "rust-test") due to 1 previous error
```

Author: taiki-e

platform-support-status-tier3.md

@@ -132,7 +132,7 @@ See [platform-support-status.md](platform-support-status.md) for Tier 1 & Tier 2
 - [x] riscv64gc-unknown-openbsd
 - [ ] riscv64imac-unknown-nuttx-elf
 - [x] s390x-unknown-linux-musl
-- [x] sparc-unknown-linux-gnu
+- [ ] sparc-unknown-linux-gnu
 - [ ] sparc-unknown-none-elf
 - [x] sparc64-unknown-netbsd
 - [x] sparc64-unknown-openbsd

tools/target-list-shared.sh

@@ -39,7 +39,7 @@ linux_gnu_targets=(
     riscv32gc-unknown-linux-gnu # tier3
     riscv64gc-unknown-linux-gnu
     s390x-unknown-linux-gnu
-    sparc-unknown-linux-gnu # tier3
+    # sparc-unknown-linux-gnu # tier3, TODO: relocations in generic ELF (EM: 18)
     sparc64-unknown-linux-gnu
     thumbv7neon-unknown-linux-gnueabihf
     x86_64-unknown-linux-gnu