fill in CC, Program, Environment.process() to get simple builds working

lib/rscons/builders/program.rb

@@ -1,19 +1,38 @@
 module Rscons
   class Program < Builder
-    def default_variables
+    def default_variables(env)
       {
-        'CC' => 'gcc',
-        'CFLAGS' => [],
-        'CPPFLAGS' => [],
+        'LD' => nil,
         'OBJSUFFIX' => '.o',
-        'CSUFFIX' => '.c',
-        'CCDEPGEN' => ['-MMD', '-MF', '$DEPFILE'],
-        'CCCOM' => ['$CC', '-c', '-o', '$TARGET', '$CCDEPGEN', '$CPPFLAGS', '$CFLAGS', '$SOURCES']
+        'LIBSUFFIX' => '.a',
+        'LDFLAGS' => [],
+        'LIBPATHS' => [],
+        'LIBS' => [],
+        'LDCOM' => ['$LD', '-o', '$TARGET', '$LDFLAGS', '$SOURCES', '-L$[LIBPATHS]', '-l$[LIBS]']
       }
     end
 
-    def produces?(target, source)
-      target.has_suffix?(@env['OBJSUFFIX']) and source.has_suffix?(@env['CSUFFIX'])
+    def run(target, sources, cache)
+      # convert sources to object file names
+      sources = sources.map do |source|
+        if source.has_suffix?([@env['OBJSUFFIX'], @env['LIBSUFFIX']])
+          source
+        else
+          o_file = source.set_suffix(@env['OBJSUFFIX', :string])
+          builder = @env.builders.values.find { |b| b.produces?(o_file, source) }
+          builder or raise "No builder found to convert input source #{source.inspect} to an object file."
+          builder.run(o_file, [source], cache)
+        end
+      end
+      unless cache.up_to_date?(target, sources)
+        vars = {
+          'TARGET' => target,
+          'SOURCES' => sources,
+          'LD' => @env['LD'] || @env['CC'], # TODO: figure out whether to use CC or CXX
+        }
+        @env.execute("LD #{target}", @env['LDCOM'], vars)
+      end
+      target
     end
   end
 end