[bazel] Move link dependencies down to where they are incurred

It wasn't clear from the docs, but linkopts are passed upstack to
dependents, so we can define them where we add source files which need
them.

No-Try: true
Change-Id: I376412682320e8802c7fd2a295a65af97650541d
Bug: skia:12541
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/527697
Reviewed-by: Leandro Lovisolo <lovisolo@google.com>
Commit-Queue: Kevin Lubick <kjlubick@google.com>

example/BUILD.bazel

@@ -6,13 +6,6 @@ cc_binary_with_flags(
     srcs = [
         "//example:HelloWorld_src",
     ],
-    linkopts = [
-        "-lX11",
-        "-lxcb",
-        "-lXau",
-        "-lXdmcp",
-        "-lGL",
-    ],
     # These flags are defined in //bazel/common_config_settings/BUILD.bazel
     set_flags = {
         # Use the GL backend with the normal GL standard (as opposed to WebGL or GLES)
@@ -40,13 +33,6 @@ cc_binary_with_flags(
     srcs = [
         "//example:HelloWorld_src",
     ],
-    linkopts = [
-        "-lX11",
-        "-lxcb",
-        "-lXau",
-        "-lXdmcp",
-        "-lX11-xcb",
-    ],
     # These flags are defined in //bazel/common_config_settings/BUILD.bazel
     set_flags = {
         "gpu_backend": [
@@ -70,13 +56,6 @@ cc_binary_with_flags(
     srcs = [
         "//example:HelloWorld_src",
     ],
-    linkopts = [
-        "-lX11",
-        "-lxcb",
-        "-lXau",
-        "-lXdmcp",
-        "-lX11-xcb",
-    ],
     # These flags are defined in //bazel/common_config_settings/BUILD.bazel
     set_flags = {
         "gpu_backend": [

src/gpu/BUILD.bazel

@@ -350,6 +350,10 @@ selects.config_setting_group(
 
 cc_library(
     name = "srcs",
+    linkopts = select({
+        "//bazel/common_config_settings:gl_backend": ["-lGL"],
+        "//conditions:default": [],
+    }),
     visibility = ["//:__subpackages__"],
     deps = [":core_srcs"] + select({
         "//bazel/common_config_settings:dawn_backend": [

tools/sk_app/BUILD.bazel

@@ -28,6 +28,18 @@ selects.config_setting_group(
 
 cc_library(
     name = "sk_app",
+    linkopts = select({
+        "@platforms//os:linux": [
+            "-lX11",
+            "-lxcb",  # dep of X11
+            "-lXau",  # dep of xcb
+            "-lXdmcp",  # dep of xcb
+        ],
+        "//conditions:default": [],
+    }) + selects.with_or({
+        (":dawn_unix", ":vulkan_unix"): ["-lX11-xcb"],
+        "//conditions:default": [],
+    }),
     visibility = ["//:__subpackages__"],
     deps = [
         ":Application_hdr",