soong: Add product variable DevicePageSizeAgnostic

The product variable DevicePageSizeAgnostic will determine
whether AOSP is kernel page size agnostic or not.

Test: source build/envsetup.sh
      lunch aosp_cf_arm64_phone_pgagnostic
      m
      cat out/soong/build.aosp_cf_arm64_phone_pgagnostic.ninja | grep __BIONIC_NO_PAGE_SIZE_MACRO
Bug: 289419664
Change-Id: I33a1a4f1967d7e78432b7b8d90357d16b2002dcc
diff --git a/cc/config/arm64_device.go b/cc/config/arm64_device.go
index ca2e05f..12722a7 100644
--- a/cc/config/arm64_device.go
+++ b/cc/config/arm64_device.go
@@ -100,7 +100,15 @@
 		return strings.Join(flags, " ")
 	})
 
-	exportedVars.ExportStringListStaticVariable("Arm64Cflags", arm64Cflags)
+	exportedVars.ExportStringList("Arm64Cflags", arm64Cflags)
+	pctx.VariableFunc("Arm64Cflags", func(ctx android.PackageVarContext) string {
+		flags := arm64Cflags
+		if ctx.Config().PageSizeAgnostic() {
+			flags = append(flags, "-D__BIONIC_NO_PAGE_SIZE_MACRO")
+		}
+		return strings.Join(flags, " ")
+	})
+
 	exportedVars.ExportStringListStaticVariable("Arm64Cppflags", arm64Cppflags)
 
 	exportedVars.ExportVariableReferenceDict("Arm64ArchVariantCflags", arm64ArchVariantCflagsVar)