Stop using deprecated __system_property_get()

If android API >= 26 (i.e. in android in-tree builds),
__system_property_read_callback() can be used instead.

Bug: 154844297
Change-Id: I9ec3d49c5e4c35281bf8405b4ae1453cd13f3179
diff --git a/BUILD b/BUILD
index 1f82fad..92c665a 100644
--- a/BUILD
+++ b/BUILD
@@ -334,6 +334,7 @@
 perfetto_filegroup(
     name = "include_perfetto_ext_base_base",
     srcs = [
+        "include/perfetto/ext/base/android_utils.h",
         "include/perfetto/ext/base/circular_queue.h",
         "include/perfetto/ext/base/container_annotations.h",
         "include/perfetto/ext/base/crash_keys.h",
@@ -638,6 +639,7 @@
 perfetto_cc_library(
     name = "src_base_base",
     srcs = [
+        "src/base/android_utils.cc",
         "src/base/crash_keys.cc",
         "src/base/ctrl_c_handler.cc",
         "src/base/event_fd.cc",