use dontBuild instead of hacks

changes:
 * buildPhase = "true"
 * buildPhase = ":"

pkgs/development/tools/analysis/clang-analyzer/default.nix

@@ -11,7 +11,8 @@ stdenv.mkDerivation rec {
 
   patches = [ ./0001-Fix-scan-build-to-use-NIX_CFLAGS_COMPILE.patch ];
   buildInputs = [ clang llvmPackages.clang perl makeWrapper ];
-  buildPhase = "true";
+
+  dontBuild = true;
 
   installPhase = ''
     mkdir -p $out/bin $out/libexec

pkgs/development/tools/build-managers/gradle/default.nix

@@ -4,7 +4,7 @@ rec {
   gradleGen = {name, src} : stdenv.mkDerivation rec {
     inherit name src;
 
-    buildPhase = ":";
+    dontBuild = true;
 
     installPhase = ''
       mkdir -pv $out/lib/gradle/

pkgs/development/tools/misc/sqitch/default.nix

@@ -1,9 +1,13 @@
 { name, stdenv, perl, makeWrapper, sqitchModule, databaseModule }:
+
 stdenv.mkDerivation {
   name = "${name}-${sqitchModule.version}";
+
   buildInputs = [ perl makeWrapper sqitchModule databaseModule ];
-  unpackPhase = ":";
-  buildPhase = ":";
+
+  src = sqitchModule;
+  dontBuild = true;
+
   installPhase = ''
     mkdir -p $out/bin
     for d in bin/sqitch etc lib share ; do