meson: Drop redundant `cpp` variable from build specification

Change-Id: I5a072ed7b73d18c7830ebe2fc464bdddc657eabb
Signed-off-by: Andrew Jeffery <andrew@codeconstruct.com.au>
diff --git a/meson.build b/meson.build
index 8f91c88..630cabe 100644
--- a/meson.build
+++ b/meson.build
@@ -33,8 +33,6 @@
     language: 'cpp',
 )
 
-cpp = meson.get_compiler('cpp')
-
 build_tests = get_option('tests')
 gpiodcxx = dependency(
     'libgpiodcxx',