zstd: Add enableStatic. See #61575

pkgs/tools/compression/zstd/default.nix

@@ -3,7 +3,8 @@
 , file
 , fetchpatch
 , legacySupport ? false
-, static ? stdenv.hostPlatform.isStatic
+, static ? stdenv.hostPlatform.isStatic # generates static libraries *only*
+, enableStatic ? static
 # these need to be ran on the host, thus disable when cross-compiling
 , buildContrib ? stdenv.hostPlatform == stdenv.buildPlatform
 , doCheck ? stdenv.hostPlatform == stdenv.buildPlatform
@@ -55,7 +56,7 @@ stdenv.mkDerivation rec {
   cmakeFlags = lib.attrsets.mapAttrsToList
     (name: value: "-DZSTD_${name}:BOOL=${if value then "ON" else "OFF"}") {
       BUILD_SHARED = !static;
-      BUILD_STATIC = static;
+      BUILD_STATIC = enableStatic;
       BUILD_CONTRIB = buildContrib;
       PROGRAMS_LINK_SHARED = !static;
       LEGACY_SUPPORT = legacySupport;