Make sure the path to the server log is absolute.

The FileSystem.getPath() API requires paths to be absolute and the path
we get for the server log might not be.  Ensure it is to avoid a crash.

Problem detected by tests that break in an upcoming change that uses the
getServerLogPath function.

RELNOTES: None.
PiperOrigin-RevId: 234192075
diff --git a/src/main/java/com/google/devtools/build/lib/runtime/BlazeRuntime.java b/src/main/java/com/google/devtools/build/lib/runtime/BlazeRuntime.java
index 0ceebc0..e6e30fa 100644
--- a/src/main/java/com/google/devtools/build/lib/runtime/BlazeRuntime.java
+++ b/src/main/java/com/google/devtools/build/lib/runtime/BlazeRuntime.java
@@ -601,7 +601,7 @@
       throw new IOException("Could not query server log location", e);
     }
 
-    return loggerFilePath.map((p) -> fileSystem.getPath(p.toString()));
+    return loggerFilePath.map((p) -> fileSystem.getPath(p.toAbsolutePath().toString()));
   }
 
   // Make sure we keep a strong reference to this logger, so that the