meson: support enableParallelChecking

This is backwards compatible, because enableParallelChecking is set by
default by stdenv if enableParallelBuilding is.

doc/hooks/meson.section.md

@@ -91,3 +91,4 @@ Meson setup hook.
 
 - `prefixKey`
 - `enableParallelBuilding`
+- `enableParallelChecking`

pkgs/by-name/me/meson/setup-hook.sh

@@ -63,9 +63,9 @@ mesonCheckPhase() {
         flagsArray+=("--timeout-multiplier=0")
     fi
 
-    # Parallel building is enabled by default.
+    # Parallel checking is enabled by default.
     local buildCores=1
-    if [ "${enableParallelBuilding-1}" ]; then
+    if [ "${enableParallelChecking-1}" ]; then
         buildCores="$NIX_BUILD_CORES"
     fi