cmd/go: add a 'buildmode' condition for script tests

In CL 208233 I am fixing a panic that occurs only with a specific
build mode. I want that test to run on all platforms that support that
build mode, but the logic for determining support is somewhat
involved.

For now, I am duplicating that logic into the cmd/internal/sys
package, which already reports platform support for other build flags.

We can refactor cmd/go/internal/work to use the extracted function in
a followup CL.

Updates #35759

Change-Id: Ibbaedde4d1e8f683c650beedd10849bc27e7a6e7
Reviewed-on: https://go-review.googlesource.com/c/go/+/208457
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Jay Conrod <jayconrod@google.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/src/cmd/go/testdata/script/README b/src/cmd/go/testdata/script/README
index 511d747129..2782a09707 100644
--- a/src/cmd/go/testdata/script/README
+++ b/src/cmd/go/testdata/script/README
@@ -79,6 +79,7 @@ should only run when the condition is satisfied. The available conditions are:
    - [symlink] for testenv.HasSymlink()
    - [exec:prog] for whether prog is available for execution (found by exec.LookPath)
    - [GODEBUG:value] for whether value is one of the comma-separated entries in the GODEBUG variable
+   - [buildmode:value] for whether -buildmode=value is supported
 
 A condition can be negated: [!short] means to run the rest of the line
 when testing.Short() is false. Multiple conditions may be given for a single