Add detection code for powerpc64le.

Originally from:

https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1019413

mesonbuild/scripts/env2mfile.py

diff --git a/mesonbuild/scripts/env2mfile.py b/mesonbuild/scripts/env2mfile.py
index 583d2bd..0d61ef8 100755
--- a/mesonbuild/scripts/env2mfile.py
+++ b/mesonbuild/scripts/env2mfile.py
@@ -135,9 +135,11 @@
     'mips64el': 'mips64',
     'i686': 'x86',
 }
+
 deb_cpu_map = {
     'armhf': 'arm7hlf',
-    'mips64el': 'mips64'
+    'mips64el': 'mips64',
+    'powerpc64le': "ppc64",
 }
 
 def deb_detect_cmake(infos: MachineInfo, data: T.Dict[str, str]) -> None: