Add the Phobos v3 unit tests to the regular unittest build.

I'm sure that we'll need to rework the build stuff at some point here
(both for Phobos v2 and v3), but this gets the v3 tests run by the v2
Makefile so that the CI will build and run them.

Author: jmdavis

Makefile

@@ -337,6 +337,7 @@ else
 unittest : unittest-debug unittest-release
 unittest-%:
 	$(MAKE) unittest OS=$(OS) MODEL=$(MODEL) DMD=$(DMD) BUILD=$*
+	DMD=$(DMD) $(DMD) -run build_v3.d unittest-$*
 endif
 
 ################################################################################

build_v3.d

@@ -3,7 +3,10 @@
 Phobos V3 Build Script
 
 Usage:
-  ./build_v3.d [debug,release,unittest]
+  ./build_v3.d [debug|release|unittest|unittest-debug|unittest-release]
+
+Environment Variables:
+  DMD=[/path/to/compiler]
 */
 
 import std.conv;
@@ -18,12 +21,23 @@ int main(string[] args)
 {
     int result = 0;
 
+    immutable compiler = environment.get("DMD", "dmd").buildNormalizedPath();
+
     bool buildUnittest = false;
     bool buildRelease = false;
-    if (args.length > 1)
+
+    if(args.length > 1)
     {
-        buildUnittest = args[1] == "unittest";
-        buildRelease = args[1] == "release";
+        switch(args[1])
+        {
+            case "release": buildRelease = true; break;
+            // This should be changed to run the tests in both debug and release
+            // modes, but that's a larger change.
+            case "unittest": buildUnittest = true; break;
+            case "unittest-debug": buildUnittest = true; break;
+            case "unittest-release": buildUnittest = true; goto case "release";
+            default: break;
+        }
     }
 
     string argFilePath = buildNormalizedPath(getcwd(), "phobosbuildargs.txt");
@@ -47,7 +61,7 @@ int main(string[] args)
         if (exists(unittestExecutable)) remove(unittestExecutable);
     }
 
-    result = runCommand("dmd --version", getcwd());
+    result = runCommand(format("%s --version", compiler), getcwd());
     if (result != 0)
     {
         writeln("Compiler Failure.");
@@ -69,7 +83,6 @@ int main(string[] args)
     {
         argFile.writeln("-main");
         argFile.writeln("-unittest");
-        argFile.writeln("-debug");
 
         version(Windows)
         {
@@ -80,24 +93,19 @@ int main(string[] args)
             argFile.writeln("-of=unittest");
         }
     }
-    else if (buildRelease)
-    {
-        argFile.writeln("-release -O");
-        argFile.writeln("-lib");
-        argFile.writeln("-of=libphobos3");
-    }
     else
     {
-        argFile.writeln("-debug");
         argFile.writeln("-lib");
-        argFile.writeln("-of=libphobos3-debug");
+        argFile.writefln("-of=libphobos3%s", buildRelease ? "" : "-debug");
     }
 
+    argFile.writeln(buildRelease ? "-release -O" : "-debug");
+
     argFile.flush();
     argFile.close();
 
     //Run the build.
-    result = runCommand("dmd @\"" ~ argFilePath ~ "\"", getcwd());
+    result = runCommand(format(`%s @"%s"`, compiler, argFilePath), getcwd());
     if (result != 0)
     {
         writeln("Build failed.");