Update `cfg` values to make buildifier happy.

PiperOrigin-RevId: 449498641
Change-Id: I145fc5dfec522753deaa64ace04ca56546351ff5
diff --git a/tools/migration/cc_toolchain_config_comparator.bzl b/tools/migration/cc_toolchain_config_comparator.bzl
index db68ca4..66746b3 100644
--- a/tools/migration/cc_toolchain_config_comparator.bzl
+++ b/tools/migration/cc_toolchain_config_comparator.bzl
@@ -46,7 +46,7 @@
         "_comparator": attr.label(
             default = ":ctoolchain_comparator",
             executable = True,
-            cfg = "host",
+            cfg = "exec",
         ),
     },
     test = True,
diff --git a/tools/migration/ctoolchain_compare.bzl b/tools/migration/ctoolchain_compare.bzl
index 3ea94f2..a9632af 100644
--- a/tools/migration/ctoolchain_compare.bzl
+++ b/tools/migration/ctoolchain_compare.bzl
@@ -42,7 +42,7 @@
         "_comparator": attr.label(
             default = ":ctoolchain_comparator",
             executable = True,
-            cfg = "host",
+            cfg = "exec",
         ),
     },
     test = True,