Add labels field to cgo_library target. (#268)

* Propagate labels on go_repo rule

* Modify string concatenation to use list and join

* Rename extraLabels -> labels

* Fix list join

* Rename arg --labels -> --label

* Add quotes around build labels

* Bump please_go version

* Undo changes to go_repo rule

* Update change log

* Add labels argument to cgo_library

* Actually use labels...

---------

Co-authored-by: mspraggs <mspraggs@thoughtmachine.net>

build_defs/cgo.build_defs

@@ -1,9 +1,25 @@
 subinclude("///go//build_defs:go", "///cc//build_defs:c")
 
-def cgo_library(name:str, srcs:list=[], resources:list=None, go_srcs:list=[], c_srcs:list=[], hdrs:list=[],
-                package:str=None, compiler_flags:list&cflags=[], linker_flags:list&ldflags=[], pkg_config:list=[],
-                subdir:str='', deps:list=[], visibility:list=None, test_only:bool&testonly=False, import_path:str='',
-                _module:str='', _subrepo:str=''):
+def cgo_library(
+    name:str,
+    srcs:list=[],
+    resources:list=None,
+    go_srcs:list=[],
+    c_srcs:list=[],
+    hdrs:list=[],
+    package:str=None,
+    compiler_flags:list&cflags=[],
+    linker_flags:list&ldflags=[],
+    pkg_config:list=[],
+    subdir:str='',
+    deps:list=[],
+    labels:list=[],
+    visibility:list=None,
+    test_only:bool&testonly=False,
+    import_path:str='',
+    _module:str='',
+    _subrepo:str='',
+):
     """Generates a Go library which can be reused by other rules.
 
     Note that by its nature this is something of a hybrid of Go and C rules. It can depend
@@ -32,6 +48,7 @@ def cgo_library(name:str, srcs:list=[], resources:list=None, go_srcs:list=[], c_
       deps (list): Dependencies. Note that if you intend to depend on cc_library rules,
                    you will likely be better off wrapping them into a cc_static_library
                    and depending on that.
+      labels (list): Labels for this rule.
       visibility (list): Visibility specification
       test_only (bool): If True, is only visible to test rules.
       import_path (str): If set, this will override the import path of the generated go package.
@@ -48,6 +65,7 @@ def cgo_library(name:str, srcs:list=[], resources:list=None, go_srcs:list=[], c_
             resources = resources,
             package = package,
             deps = deps,
+            labels = labels,
             import_path = import_path,
             visibility = visibility,
             test_only = test_only,
@@ -107,6 +125,7 @@ def cgo_library(name:str, srcs:list=[], resources:list=None, go_srcs:list=[], c_
         pkg_config_libs = pkg_config,
         test_only = test_only,
         deps = deps,
+        labels = labels,
     )
     go_rule = go_library(
         name = f'_{name}#go',
@@ -119,6 +138,7 @@ def cgo_library(name:str, srcs:list=[], resources:list=None, go_srcs:list=[], c_
         import_path=import_path,
         _subrepo = _subrepo,
         _module = _module,
+        labels = labels,
     )
 
     output = package if package else name
@@ -129,6 +149,7 @@ def cgo_library(name:str, srcs:list=[], resources:list=None, go_srcs:list=[], c_
         outs = [f'{output}.importconfig'],
         visibility=visibility,
         test_only=test_only,
+        labels = labels,
     )
 
     # And finally combine the compiled C code into the Go archive object so go tool link can find it later.
@@ -140,7 +161,7 @@ def cgo_library(name:str, srcs:list=[], resources:list=None, go_srcs:list=[], c_
         test_only = test_only,
         linker_flags = linker_flags,
         package = package,
-        labels = ['link:plz-out/go/pkg/%s_%s' % (CONFIG.OS, CONFIG.ARCH)],
+        labels = ['link:plz-out/go/pkg/%s_%s' % (CONFIG.OS, CONFIG.ARCH)] + labels,
         provides = {
             'go': ':' + name,
             'go_src': go_rule,

build_defs/go.build_defs

@@ -254,6 +254,7 @@ def go_library(name:str, srcs:list, resources:list=[], asm_srcs:list=None, hdrs:
                     code that you never want to be instrumented.
       filter_srcs (bool): If True, filters source files through Go's standard build constraints.
       import_path (str): If set, this will override the import path of the generated go package.
+      labels (list): Labels for this rule.
       package (str): The package as it would appear at the top of the go source files. Defaults
                      to name.
       pgo_file (str): The CPU profile to supply for profile-guided optimisation.