Roll ICU to 715ec351
* 715ec351 Do not use check_thin_archive in the Fuchsia build
* 84fb34e2 Revert "Set icu_disable_thin_archive on non-component chromeos builds"
* c18a1176 Update IANA timezone db to 2020b
* 146cb611 Set icu_disable_thin_archive on non-component chromeos builds
* aba3f0df Add rbns/zh.res rbns/ja.res to fix DateTimeFormat
* 3c77cb51 Pass -fvisibility=hidden on Fuchsia
* aef20f06 Fix the build config regarding icu_disable_thin_archive
Change-Id: I9a59b8fcf5ca48b8a3fa3adc432f166a65bfa73d