Do not use prefixed clang for wasi

Rust 1.68 (rust-lang/rust#106489) broke this:

```
= note: clang-15: error: unsupported option '--export'
        clang-15: error: unsupported option '--stack-first'
        clang-15: error: unsupported option '--allow-undefined'
        clang-15: error: unsupported option '--fatal-warnings'
        clang-15: error: unsupported option '--no-demangle'
        clang-15: error: unsupported option '--gc-sections'
        clang-15: error: unknown argument: '-flavor'
        clang-15: error: no such file or directory: 'wasm'
        clang-15: error: no such file or directory: '__main_void'
```

Author: taiki-e

.github/workflows/ci.yml

@@ -96,17 +96,7 @@ jobs:
           # WASI
           # rustup target list | grep -e '-wasi'
           # rustc --print target-list | grep -e '-wasi'
-          # TODO(wasi):
-          # = note: clang-15: error: unsupported option '--export'
-          #         clang-15: error: unsupported option '--stack-first'
-          #         clang-15: error: unsupported option '--allow-undefined'
-          #         clang-15: error: unsupported option '--fatal-warnings'
-          #         clang-15: error: unsupported option '--no-demangle'
-          #         clang-15: error: unsupported option '--gc-sections'
-          #         clang-15: error: unknown argument: '-flavor'
-          #         clang-15: error: no such file or directory: 'wasm'
-          #         clang-15: error: no such file or directory: '__main_void'
-          # - wasm32-wasi
+          - wasm32-wasi
         os:
           - ubuntu-22.04
           - ubuntu-20.04

CHANGELOG.md

@@ -10,6 +10,8 @@ Note: In this file, do not use the hard wrap in the middle of a sentence for com
 
 ## [Unreleased]
 
+- Fix linker error for wasm32-wasi on Rust 1.68+.
+
 ## [1.6.1] - 2022-12-13
 
 - Improve robustness for temporary network failures.

main.sh

@@ -112,7 +112,7 @@ install_rust_cross_toolchain() {
         *) qemu_ld_prefix="${toolchain_dir}/${target}" ;;
     esac
     case "${target}" in
-        *-freebsd | *-wasi)
+        *-freebsd)
             cat >>"${GITHUB_ENV}" <<EOF
 CARGO_TARGET_${target_upper}_LINKER=${target}-clang
 CC_${target_lower}=${target}-clang
@@ -124,6 +124,20 @@ STRIP=llvm-strip
 OBJCOPY=llvm-objcopy
 OBJDUMP=llvm-objdump
 READELF=llvm-readelf
+EOF
+            ;;
+        *-wasi)
+            cat >>"${GITHUB_ENV}" <<EOF
+CARGO_TARGET_${target_upper}_LINKER=clang
+CC_${target_lower}=clang
+CXX_${target_lower}=clang++
+AR_${target_lower}=llvm-ar
+AR=llvm-ar
+NM=llvm-nm
+STRIP=llvm-strip
+OBJCOPY=llvm-objcopy
+OBJDUMP=llvm-objdump
+READELF=llvm-readelf
 EOF
             ;;
         *)