Revert "[coverage] Remove cmx coverage support from GN SDK"

This reverts commit baa41ae.

Reason for revert: broke Chromium coverage builder not detected by fx lsc

Original change's description:
> [coverage] Remove cmx coverage support from GN SDK
>
> Only one OOT cmx test that uses this left, and it's on its way out.
> Drop some tech debt baggage.
>
> See also:
> https://groups.google.com/a/google.com/g/fuchsia-cmxtinction/c/mL1CfpIW2PY/m/L17w3m8JBgAJ
>
> Change-Id: I4ed6897b1ea705778a2f41fdb3f5046e5e5b7c2d
> Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/732824
> Commit-Queue: Shai Barack <shayba@google.com>
> Fuchsia-Auto-Submit: Shai Barack <shayba@google.com>
> Reviewed-by: Clayton Wilkinson <wilkinsonclay@google.com>

Change-Id: I928b65804790f6a7468cb7bbde2462e11f2f6aad
Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/742744
Fuchsia-Auto-Submit: Shai Barack <shayba@google.com>
Reviewed-by: Greg Thompson <grt@google.com>
Reviewed-by: RubberStamper 🤖 <android-build-ayeaye@system.gserviceaccount.com>
Commit-Queue: Auto-Submit <auto-submit@fuchsia-infra.iam.gserviceaccount.com>

Author: shaybarak

scripts/sdk/gn/base/build/component.gni

@@ -126,21 +126,38 @@ template("fuchsia_component") {
     _manifest_version = "v2"
   }
 
-  if (fuchsia_code_coverage && _manifest_version == "v2") {
-    merged_manifest = "${target_name}-coverage.cml"
-    cmc_merge(merged_manifest) {
-      forward_variables_from(invoker,
-                             [
-                               "deps",
-                               "testonly",
-                             ])
-      sources = [
-        "${fuchsia_sdk}/build/enable_coverage_data.cml",
-        manifest,
-      ]
-      output_name = merged_manifest
+  if (fuchsia_code_coverage) {
+    if (_manifest_version == "v1") {
+      merged_manifest = "${target_name}-coverage.cmx"
+      cmc_merge(merged_manifest) {
+        forward_variables_from(invoker,
+                               [
+                                 "deps",
+                                 "testonly",
+                               ])
+        sources = [
+          "${fuchsia_sdk}/build/enable_coverage_data.cmx",
+          manifest,
+        ]
+        output_name = merged_manifest
+      }
+      manifest = "${target_out_dir}/${merged_manifest}"
+    } else if (_manifest_version == "v2") {
+      merged_manifest = "${target_name}-coverage.cml"
+      cmc_merge(merged_manifest) {
+        forward_variables_from(invoker,
+                               [
+                                 "deps",
+                                 "testonly",
+                               ])
+        sources = [
+          "${fuchsia_sdk}/build/enable_coverage_data.cml",
+          manifest,
+        ]
+        output_name = merged_manifest
+      }
+      manifest = "${target_out_dir}/${merged_manifest}"
     }
-    manifest = "${target_out_dir}/${merged_manifest}"
   }
 
   # The component manifest validated using cmx_validation for v1,

scripts/sdk/gn/base/build/enable_coverage_data.cmx

@@ -0,0 +1,7 @@
+{
+    "sandbox": {
+        "services": [
+            "fuchsia.debugdata.Publisher"
+        ]
+    }
+}

scripts/sdk/gn/base/build/gn-rules-meta.json

@@ -1,25 +1,26 @@
 {
-    "docs": [
-        "build/BUILD.gn",
-        "build/build_id_dir.gni",
-        "build/cipd.gni",
-        "build/cmc.gni",
-        "build/config/BUILD.gn",
-        "build/config/config.gni",
-        "build/enable_coverage_data.cml",
-        "build/fuchsia_sdk_pkg.gni",
-        "build/gn_run_binary.py",
-        "build/fidl_library.gni",
-        "build/gen_fidl_response_file.py",
-        "build/package.gni",
-        "build/component.gni",
-        "build/populate_build_id_dir.py",
-        "build/prepare_cipd_package_definition.py",
-        "build/prepare_package_inputs.py",
-        "build/pm_tool.gni",
-        "build/test_targets.gni",
-        "build/test.gni"
-    ],
-    "name": "gn-rules",
-    "type": "documentation"
+  "docs": [
+    "build/BUILD.gn",
+    "build/build_id_dir.gni",
+    "build/cipd.gni",
+    "build/cmc.gni",
+    "build/config/BUILD.gn",
+    "build/config/config.gni",
+    "build/enable_coverage_data.cml",
+    "build/enable_coverage_data.cmx",
+    "build/fuchsia_sdk_pkg.gni",
+    "build/gn_run_binary.py",
+    "build/fidl_library.gni",
+    "build/gen_fidl_response_file.py",
+    "build/package.gni",
+    "build/component.gni",
+    "build/populate_build_id_dir.py",
+    "build/prepare_cipd_package_definition.py",
+    "build/prepare_package_inputs.py",
+    "build/pm_tool.gni",
+    "build/test_targets.gni",
+    "build/test.gni"
+  ],
+  "name": "gn-rules",
+  "type": "documentation"
 }