Always enable cgo in builds made with bazel

This might make cross compiling a bit more difficult, but it is less
surprising when you know cgo will be enabled if it builds.

Background in buchgr#655.

BUILD.bazel

@@ -48,6 +48,7 @@ go_binary(
     name = "bazel-remote",
     embed = [":go_default_library"],
     pure = "off",
+    cgo = True,
     static = "off",
     visibility = ["//visibility:public"],
     x_defs = {"main.gitCommit": "{STABLE_GIT_COMMIT}"},
@@ -59,6 +60,7 @@ go_binary(
     goarch = "amd64",
     goos = "linux",
     pure = "off",
+    cgo = True,
     static = "off",
     visibility = ["//visibility:public"],
     x_defs = {"main.gitCommit": "{STABLE_GIT_COMMIT}"},
@@ -69,7 +71,8 @@ go_binary(
     embed = [":go_default_library"],
     goarch = "arm64",
     goos = "linux",
-    pure = "on",
+    pure = "off",
+    cgo = True,
     static = "on",
     visibility = ["//visibility:public"],
     x_defs = {"main.gitCommit": "{STABLE_GIT_COMMIT}"},
@@ -80,7 +83,8 @@ go_binary(
     embed = [":go_default_library"],
     goarch = "amd64",
     goos = "darwin",
-    pure = "on",
+    pure = "off",
+    cgo = True,
     static = "on",
     visibility = ["//visibility:public"],
     x_defs = {"main.gitCommit": "{STABLE_GIT_COMMIT}"},
@@ -91,7 +95,8 @@ go_binary(
     embed = [":go_default_library"],
     goarch = "arm64",
     goos = "darwin",
-    pure = "on",
+    pure = "off",
+    cgo = True,
     static = "on",
     visibility = ["//visibility:public"],
     x_defs = {"main.gitCommit": "{STABLE_GIT_COMMIT}"},
@@ -107,6 +112,7 @@ go_image(
     goarch = "amd64",
     goos = "linux",
     pure = "off",
+    cgo = True,
     static = "on",
     visibility = ["//visibility:private"],
     x_defs = {"main.gitCommit": "{STABLE_GIT_COMMIT}"},
@@ -119,6 +125,7 @@ go_image(
     goarch = "arm64",
     goos = "linux",
     pure = "off",
+    cgo = True,
     static = "on",
     visibility = ["//visibility:private"],
     x_defs = {"main.gitCommit": "{STABLE_GIT_COMMIT}"},