pw_toolchain: Use %package% for cxx_builtin_include_directories

Switches the linux sysroot to use %package% pattern for
cxx_builtin_include_directories to match %sysroot% instances.

Change-Id: I6b7ee553504c08ca13b0bf68456c2bc7a6ca9244
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/168340
Reviewed-by: Ted Pudlik <tpudlik@google.com>
Presubmit-Verified: CQ Bot Account <pigweed-scoped@luci-project-accounts.iam.gserviceaccount.com>
Pigweed-Auto-Submit: Armando Montanez <amontanez@google.com>
Commit-Queue: Auto-Submit <auto-submit@pigweed-service-accounts.iam.gserviceaccount.com>
diff --git a/pw_toolchain/host_clang/BUILD.bazel b/pw_toolchain/host_clang/BUILD.bazel
index 046991a..7825652 100644
--- a/pw_toolchain/host_clang/BUILD.bazel
+++ b/pw_toolchain/host_clang/BUILD.bazel
@@ -38,9 +38,9 @@
     name = "linux_sysroot",
     builtin_sysroot = "external/linux_sysroot",
     cxx_builtin_include_directories = [
-        "@llvm_toolchain//:include/x86_64-unknown-linux-gnu/c++/v1",
-        "@llvm_toolchain//:include/c++/v1",
-        "@llvm_toolchain//:lib/clang/17/include",
+        "%package(@llvm_toolchain//)%/include/x86_64-unknown-linux-gnu/c++/v1",
+        "%package(@llvm_toolchain//)%/include/c++/v1",
+        "%package(@llvm_toolchain//)%/lib/clang/17/include",
         "%sysroot%/usr/local/include",
         "%sysroot%/usr/include/x86_64-linux-gnu",
         "%sysroot%/usr/include",