Delegate coverage tools to @remote_coverage_tools

Requires:
 - bazelbuild#10379 is merged
 - a new remote coverage tools zip pushed
 - coverage.WORKSPACE updated to the new tools

This changes the @bazel_tools//tools/test/BUILD file to fully delegate to the @remote_coverage_tools repository, which must contain rules for :lcov_merger and :coverage_report_generator.

This makes the @remote_coverage_tools reference self-contained, which allows overriding the tools using --override_repository, and allows independently replacing or fixing them.

Progress on bazelbuild#4685.

Change-Id: I321c62332f00d910f4ccfb3244d63e60627d59ad

Author: ulfjack

src/main/java/com/google/devtools/build/lib/analysis/BaseRuleClasses.java

@@ -104,7 +104,7 @@ public static LabelLateBoundDefault<TestConfiguration> coverageSupportAttribute(
       "//tools/test:coverage_report_generator";
 
   private static final String DEFAULT_COVERAGE_OUTPUT_GENERATOR_VALUE =
-      "@bazel_tools//tools/test/CoverageOutputGenerator/java/com/google/devtools/coverageoutputgenerator:Main";
+      "@bazel_tools//tools/test:lcov_merger";
 
   @AutoCodec
   static final Resolver<TestConfiguration, Label> COVERAGE_REPORT_GENERATOR_CONFIGURATION_RESOLVER =

tools/BUILD

@@ -61,7 +61,6 @@ filegroup(
         "//tools/python:embedded_tools",
         "//tools/runfiles:embedded_tools",
         "//tools/test:embedded_tools",
-        "//tools/test/CoverageOutputGenerator/java/com/google/devtools/coverageoutputgenerator:embedded_tools",
         "//tools/osx/crosstool:srcs",
         "//tools/osx:srcs",
         "//tools/sh:embedded_tools",

tools/test/BUILD.tools

@@ -33,9 +33,14 @@ filegroup(
     srcs = ["collect_coverage.sh"],
 )
 
-filegroup(
+alias(
     name = "coverage_report_generator",
-    srcs = ["@bazel_tools//tools/test/CoverageOutputGenerator/java/com/google/devtools/coverageoutputgenerator:Main"],
+    actual = "@remote_coverage_tools//:coverage_report_generator",
+)
+
+alias(
+    name = "lcov_merger",
+    actual = "@remote_coverage_tools//:lcov_merger",
 )
 
 filegroup(

tools/test/CoverageOutputGenerator/java/com/google/devtools/coverageoutputgenerator/BUILD

@@ -170,11 +170,3 @@ filegroup(
     srcs = glob(["**"]),
     visibility = ["//visibility:public"],
 )
-
-filegroup(
-    name = "embedded_tools",
-    srcs = [
-        "BUILD.tools",
-    ],
-    visibility = ["//visibility:public"],
-)