Import cpu detection fix from Debian.

https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1033579

mesonbuild/scripts/env2mfile.py

diff --git a/mesonbuild/scripts/env2mfile.py b/mesonbuild/scripts/env2mfile.py
index 015763c..92031e9 100755
--- a/mesonbuild/scripts/env2mfile.py
+++ b/mesonbuild/scripts/env2mfile.py
@@ -134,6 +134,7 @@
 deb_cpu_family_map = {
     'mips64el': 'mips64',
     'i686': 'x86',
+    'powerpc64le': "ppc64",
 }
 
 deb_cpu_map = {