Inline usages of LOCAL_STEM

Having no variables in include/inherit-product statements
makes the conversion to starlark cleaner.

Bug: 211659921
Test: Presubmits
Change-Id: I59ad9a2800619a35fa51fe03b9ad7e9de4611466
diff --git a/self-extractors/root/proprietary/BoardConfigVendor.mk b/self-extractors/root/proprietary/BoardConfigVendor.mk
index fbf6e0f..6a023d4 100644
--- a/self-extractors/root/proprietary/BoardConfigVendor.mk
+++ b/self-extractors/root/proprietary/BoardConfigVendor.mk
@@ -12,7 +12,5 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-LOCAL_STEM := sunfish/BoardConfigPartial.mk
-
--include vendor/google_devices/$(LOCAL_STEM)
--include vendor/qcom/$(LOCAL_STEM)
+-include vendor/google_devices/sunfish/BoardConfigPartial.mk
+-include vendor/qcom/sunfish/BoardConfigPartial.mk
diff --git a/self-extractors/root/proprietary/device-vendor.mk b/self-extractors/root/proprietary/device-vendor.mk
index 7b0de3f..c75a411 100644
--- a/self-extractors/root/proprietary/device-vendor.mk
+++ b/self-extractors/root/proprietary/device-vendor.mk
@@ -12,7 +12,5 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-LOCAL_STEM := sunfish/device-partial.mk
-
-$(call inherit-product-if-exists, vendor/google_devices/$(LOCAL_STEM))
-$(call inherit-product-if-exists, vendor/qcom/$(LOCAL_STEM))
+$(call inherit-product-if-exists, vendor/google_devices/sunfish/device-partial.mk)
+$(call inherit-product-if-exists, vendor/qcom/sunfish/device-partial.mk)