Signed-off-by: Doug Nazar <nazard@nazar.ca>

Xavier Claessens authored 4 years ago and Ralph Giles committed 4 years ago

meson.source_root() and meson.build_root() have been deprecated in
latest Meson release because they are a trap. They point to the root of
parent project instead of root of current subproject. Meson 0.56.0 added
meson.project_source/build_root() but it is just as easy to use
meson.current_source/build_dir() in the root meson.build file and avoids
bumping required meson version.

Signed-off-by: Ralph Giles <giles@thaumas.net>

Tested on:
 - Linux/x86* with gcc
 - Android armv7 arm64 x86 x86_64 with clang
 - Windows x86 x86_64 with Visual Studio 2017
 - Windows x86 x86_64 with MinGW
 - macOS x86_64 with clang
 - iOS arm64 x86_64 with clang

Co-authored by: Nirbheek Chauhan <nirbheek@centricular.com>

https://gitlab.xiph.org/xiph/opus/-/merge_requests/13