Drop coverage linker flags from stdlib build

We never compile CGo with coverage instrumentation and the stdlib
contains no user-provided C/C++ code, so linking coverage runtimes is
never needed.

go/private/actions/stdlib.bzl

@@ -12,6 +12,10 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+load(
+    "//go/private:common.bzl",
+    "COVERAGE_OPTIONS_DENYLIST",
+)
 load(
     "//go/private:providers.bzl",
     "GoStdLib",
@@ -96,10 +100,12 @@ def _build_stdlib(go):
     else:
         # NOTE(#2545): avoid unnecessary dynamic link
         # go std library doesn't use C++, so should not have -lstdc++
+        # Also drop coverage flags as nothing in the stdlib is compiled with
+        # coverage - we disable it for all CGo code anyway.
         ldflags = [
             option
             for option in extldflags_from_cc_toolchain(go)
-            if option not in ("-lstdc++", "-lc++")
+            if option not in ("-lstdc++", "-lc++") and option not in COVERAGE_OPTIONS_DENYLIST
         ]
         env.update({
             "CGO_ENABLED": "1",

go/private/common.bzl

@@ -243,3 +243,12 @@ def count_group_matches(v, prefix, suffix):
         count = count + 1
 
     return count
+
+# C/C++ compiler and linker options related to coverage instrumentation.
+COVERAGE_OPTIONS_DENYLIST = {
+    "--coverage": None,
+    "-ftest-coverage": None,
+    "-fprofile-arcs": None,
+    "-fprofile-instr-generate": None,
+    "-fcoverage-mapping": None,
+}

go/private/context.bzl

@@ -55,6 +55,7 @@ load(
     "goos_to_extension",
     "goos_to_shared_extension",
     "is_struct",
+    "COVERAGE_OPTIONS_DENYLIST",
 )
 load(
     "//go/platform:apple.bzl",
@@ -86,7 +87,7 @@ _UNSUPPORTED_C_COMPILERS = {
     "clang-cl": None,
 }
 
-_COMPILER_OPTIONS_DENYLIST = {
+_COMPILER_OPTIONS_DENYLIST = dict({
     # cgo parses the error messages from the compiler.  It can't handle colors.
     # Ignore both variants of the diagnostics color flag.
     "-fcolor-diagnostics": None,
@@ -107,7 +108,7 @@ _COMPILER_OPTIONS_DENYLIST = {
     "-fprofile-arcs": None,
     "-fprofile-instr-generate": None,
     "-fcoverage-mapping": None,
-}
+}, **COVERAGE_OPTIONS_DENYLIST)
 
 _LINKER_OPTIONS_DENYLIST = {
     "-Wl,--gc-sections": None,