Pass -isysroot to the linker when running compiletests too

Without this, rustc will fail to perform linking. So we need to pass
this to steps where we _use_ the built rustc, not just where we are
building it.

Bug: 1386212
Change-Id: I842ecc8734df1a5614e02da703bf447d41bbfe3c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4220014
Commit-Queue: danakj <[email protected]>
Reviewed-by: Hans Wennborg <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1102337}
NOKEYCHECK=True
GitOrigin-RevId: e8e683582006c7816da596d581c984144d3d4190

Author: danakj

build_rust.py

@@ -162,7 +162,7 @@ def FetchCargo(rust_git_hash):
         target = 'cargo-beta-x86_64-pc-windows-msvc'
     elif sys.platform == 'darwin':
         if platform.machine() == 'arm64':
-            target = 'rust-std-beta-aarch64-apple-darwin'
+            target = 'cargo-beta-aarch64-apple-darwin'
         else:
             target = 'cargo-beta-x86_64-apple-darwin'
     else:
@@ -237,6 +237,7 @@ def RunXPy(sub, args, llvm_bins_path, zlib_path, libxml2_dirs, build_mac_arm,
         'CFLAGS',
         'CXXFLAGS',
         'LDFLAGS',
+        'RUSTFLAGS',
         'RUSTFLAGS_BOOTSTRAP',
         'RUSTFLAGS_NOT_BOOTSTRAP',
         'RUSTDOCFLAGS',
@@ -273,6 +274,10 @@ def RunXPy(sub, args, llvm_bins_path, zlib_path, libxml2_dirs, build_mac_arm,
             f' -Clink-arg=-isysroot -Clink-arg={sdk_path}')
         RUSTENV['RUSTFLAGS_NOT_BOOTSTRAP'] += (
             f' -Clink-arg=-isysroot -Clink-arg={sdk_path}')
+        # This flag needs to be in RUSTFLAGS for running compiletests as well,
+        # for building things _with_ rustc, not just for building rustc.
+        RUSTENV['RUSTFLAGS'] += (
+            f' -Clink-arg=-isysroot -Clink-arg={sdk_path}')
 
     if zlib_path:
         RUSTENV['CFLAGS'] += f' -I{zlib_path}'