lineage: soong: Add var for linker shim libs

* To limit security exposure, we're forcing all devices
  to define shim libs with a TARGET_LD_SHIM_LIBS

Change-Id: Ic8722c42807429f2faa3546316c71c40533ce195
diff --git a/build/soong/android/variable.go b/build/soong/android/variable.go
index 221bf97..85f7dee 100644
--- a/build/soong/android/variable.go
+++ b/build/soong/android/variable.go
@@ -9,6 +9,9 @@
 	Uses_qcom_bsp_legacy struct {
 		Cppflags []string
 	}
+	Target_shim_libs struct {
+		Cppflags []string
+	}
 }
 
 type ProductVariables struct {
@@ -16,4 +19,5 @@
 	Specific_camera_parameter_library  *string `json:",omitempty"`
 	Needs_text_relocations  *bool `json:",omitempty"`
 	Uses_qcom_bsp_legacy  *bool `json:",omitempty"`
+	Target_shim_libs  *string `json:",omitempty"`
 }