bazel: require setting cockroach_cross=y to opt into cross toolchains

With `--incompatible_enable_cc_toolchain_resolution` set in cockroachdb#73819, now
Bazel selects the appropriate toolchain for you. Bazel was selecting the
`cross_linux_toolchain` when building for the host platform on Linux,
resulting in link errors when trying to compile `stress` under `race`.
We update the toolchains to instead require opting into the cross
toolchains by defining `cockroach_cross=y`.

Closes cockroachdb#73997.

Release note: None

build/toolchains/BUILD.bazel

@@ -8,6 +8,9 @@ toolchain(
         "@platforms//os:linux",
         "@platforms//cpu:x86_64",
     ],
+    target_settings = [
+        ":cross",
+    ],
     toolchain = "@toolchain_cross_x86_64-unknown-linux-gnu//:toolchain",
     toolchain_type = "@bazel_tools//tools/cpp:toolchain_type",
 )
@@ -30,6 +33,9 @@ toolchain(
         "@platforms//os:windows",
         "@platforms//cpu:x86_64",
     ],
+    target_settings = [
+        ":cross",
+    ],
     toolchain = "@toolchain_cross_x86_64-w64-mingw32//:toolchain",
     toolchain_type = "@bazel_tools//tools/cpp:toolchain_type",
 )
@@ -52,6 +58,9 @@ toolchain(
         "@platforms//os:macos",
         "@platforms//cpu:x86_64",
     ],
+    target_settings = [
+        ":cross",
+    ],
     toolchain = "@toolchain_cross_x86_64-apple-darwin19//:toolchain",
     toolchain_type = "@bazel_tools//tools/cpp:toolchain_type",
 )
@@ -74,6 +83,9 @@ toolchain(
         "@platforms//os:linux",
         "@platforms//cpu:arm64",
     ],
+    target_settings = [
+        ":cross",
+    ],
     toolchain = "@toolchain_cross_aarch64-unknown-linux-gnu//:toolchain",
     toolchain_type = "@bazel_tools//tools/cpp:toolchain_type",
 )
@@ -138,6 +150,13 @@ config_setting(
     },
 )
 
+config_setting(
+    name = "cross",
+    define_values = {
+        "cockroach_cross": "y",
+    },
+)
+
 config_setting(
     name = "is_cross_macos",
     constraint_values = [

pkg/cmd/github-pull-request-make/main.go

@@ -294,6 +294,11 @@ func main() {
 					}
 				}
 				args = append(args, "--")
+				if target == "stressrace" {
+					args = append(args, "--config=race")
+				} else {
+					args = append(args, "--test_sharding_strategy=disabled")
+				}
 				var filters []string
 				for _, test := range pkg.tests {
 					filters = append(filters, "^"+test+"$")
@@ -304,11 +309,6 @@ func main() {
 				// Give the entire test 1 more minute than the duration to wrap up.
 				args = append(args, fmt.Sprintf("--test_timeout=%d", int((duration+1*time.Minute).Seconds())))
 				args = append(args, "--run_under", fmt.Sprintf("%s -stderr -maxfails 1 -maxtime %s -p %d", bazelStressTarget, duration, parallelism))
-				if target == "stressrace" {
-					args = append(args, "--config=race")
-				} else {
-					args = append(args, "--test_sharding_strategy=disabled")
-				}
 				// NB: bazci is expected to be put in `PATH` by the caller.
 				cmd := exec.Command("bazci", args...)
 				cmd.Stdout = os.Stdout