Fix bazel_toolchain_test

This time for real. This rolls back bea9c01592a5, my previous attempt to fix
the test. What happened:

Before fdba19031961:
The BUILD file was referencing the data as a directory, and the sandbox
implementation was symlinking the entire directory (not individual files).
As a result, the chmod call was succeeding, but *it was modifying the source
tree*!

After fdba19031961, before bea9c01592a5:
The BUILD file was using a glob to enumerate individual files, and the
individual symlinks in the sandbox are in a read-only file system. The chmod
call was failing.

After bea9c01592a5:
Without the chmod call, the test passed because the files were still marked
as executable *in the source tree* due to the pre-fdba19031961 code. However,
it failed in a clean checkout.

Solution:
Reinstate the chmod call, but make sure all the files are copied into a
temporary *empty* directory.

Fixes #2891.

PiperOrigin-RevId: 154436636

src/test/shell/bazel/BUILD

diff --git a/src/test/shell/bazel/BUILD b/src/test/shell/bazel/BUILD
index 2b0b4f36..26b92f3 100644
--- a/src/test/shell/bazel/BUILD
+++ b/src/test/shell/bazel/BUILD
@@ -154,7 +154,6 @@
         "//conditions:default": ["//src/test/shell/bazel/testdata:bazel_toolchain_test_project_pkg"],
     }),
     tags = [
-        "noci",  # TODO(ulfjack): Re-enable for CI once https://github.com/bazelbuild/bazel/issues/2891 is fixed.
         "requires-network",
     ],
 )

src/test/shell/bazel/bazel_toolchain_test.sh

diff --git a/src/test/shell/bazel/bazel_toolchain_test.sh b/src/test/shell/bazel/bazel_toolchain_test.sh
index d7e8e31..cb5a8bf 100755
--- a/src/test/shell/bazel/bazel_toolchain_test.sh
+++ b/src/test/shell/bazel/bazel_toolchain_test.sh
@@ -27,8 +27,14 @@
   exit 0
 fi
 
+# Run in a temporary directory!
+mkdir -p "${TEST_TMPDIR}/TEMP_TEMP_TEMP"
+cd "${TEST_TMPDIR}/TEMP_TEMP_TEMP"
+
 # Copy the project package here
-cp -r ${testdata_path}/bazel_toolchain_test_data/* .
+# We must use -L here; the files may be symlinks into the source tree, which we
+# could inadvertantly modify below.
+cp -rL ${testdata_path}/bazel_toolchain_test_data/* .
 
 # Rename WORKSPACE.linaro file to WORKSPACE
 # (Did not include the file WORKSPACE in the test because source tree under
@@ -40,6 +46,9 @@
   mv "$i" "$(dirname "$i")/BUILD"
 done
 
+# Make sure that the wrapper scripts have the execution permission
+chmod +x tools/arm_compiler/linaro_linux_gcc/arm-linux-gnueabihf-*
+
 bazel clean --expunge
 bazel build --crosstool_top=//tools/arm_compiler:toolchain --cpu=armeabi-v7a \
   --spawn_strategy=standalone hello || fail "Should build"