Remove direct reference to genfiles

For historical reasons, Bazel has two directories for generated files,
although a future version of Bazel will remove the genfiles directory:
bazelbuild/bazel#6761

Currently, rosmsg() copies all the source files (*.msg, *.srv) to the
output directory, so that the directory structure matches the needs of
ROS's codegen tools. It uses a hacky way of finding the paths to the
transitive dependencies within the output directory, which includes a
direct reference to genfiles. By using output_to_bindir=True, we can
avoid the direct reference.

Fixing the hack would involve rewriting the rosmsg() macro to use a
rule, which wouldn't be too hard but might break compatibility.

See #2.

Change-Id: Ibae3451e1329e397329089aa6796c5477789c788

bazel/build_rules/rosmsg.bzl

@@ -8,11 +8,11 @@ OUTPUT_PREFIX = "__rosmsg__"
 _COMMON_CMD_CODE = """
 # Find all directories with *.msg *.srv files. The names of these directories
 # are assumed to be the package names for the inclusion search paths.
-# _CopyMsgSrvFiles ensures all such files are within genfiles, although
+# _CopyMsgSrvFiles ensures all such files are within bindir, although
 # depending on the execution settings they may be found in the host or target
-# genfiles.
-# TODO(rodrigoq): use aspects for the include directories instead of find(1).
-ROS_INCLUDE_DIRS=( $$(find $(GENDIR) bazel-out/host/genfiles \\
+# bindir.
+# TODO(rodrigoq): use providers for the include directories instead of find(1).
+ROS_INCLUDE_DIRS=( $$(find $(GENDIR) bazel-out/host/bin \\
     \( -name "*.msg" -or -name "*.srv" \) \\
     -exec dirname {{}} \; | sort -u) )
 
@@ -131,6 +131,7 @@ def _CopyMsgSrvFiles(name, srcs, output_dir):
             srcs = [src],
             outs = [new_path],
             cmd = "cp $< $@",
+            output_to_bindir = True,
         )
         results.append(new_path)
     return results