Coverage implementation for Objective C.

Added gcnoFile() to translate a source file to its corrosponding .gcno file.
Added "-fprofile-arcs", "-ftest-coverage", "-fprofile-dir=./coverage_output" to compiler flags when compiling in coverage mode.
Added "-fprofile-arcs", "-ftest-coverage" to linker flags when linking in coverage mode.
Added constructor for InstrumentedFilesProviderImpl that was recently removed due to being unused in [].
Added .gcno files to runfiles of IosTest runner to be used by gcov after tests have been run.

This CL + [] will enable blaze coverage will work on an ios_test target.

An example of the [] output of this change + [] is

--
MOS_MIGRATED_REVID=86601223

1 files changed, 6 insertions, 0 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/rules/test/InstrumentedFilesProviderImpl.java b/src/main/java/com/google/devtools/build/lib/rules/test/InstrumentedFilesProviderImpl.java
index 1452e2db43..ad5f333197 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/test/InstrumentedFilesProviderImpl.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/test/InstrumentedFilesProviderImpl.java
@@ -36,6 +36,12 @@ public final class InstrumentedFilesProviderImpl implements InstrumentedFilesPro
   private final NestedSet<Artifact> instrumentedFiles;
   private final NestedSet<Artifact> instrumentationMetadataFiles;
 
+  public InstrumentedFilesProviderImpl(NestedSet<Artifact> instrumentedFiles,
+      NestedSet<Artifact> instrumentationMetadataFiles) {
+    this.instrumentedFiles = instrumentedFiles;
+    this.instrumentationMetadataFiles = instrumentationMetadataFiles;
+  }
+
   public InstrumentedFilesProviderImpl(InstrumentedFilesCollector collector) {
     this.instrumentedFiles = collector.getInstrumentedFiles();
     this.instrumentationMetadataFiles = collector.getInstrumentationMetadataFiles();