Add shortcut method for creating environments - close #149

Add env() method to create environments.
Process all environments created at build script top level before
executing any autoconf-enabled tasks, or if no tasks are specified by
the user.

build_tests/two_sources/Rsconscript

@@ -1,6 +1,4 @@
-default do
-  Environment.new(echo: :command) do |env|
-    env.Object("one.o", "one.c", 'CPPFLAGS' => ['-DONE'])
-    env.Program('two_sources.exe', ['one.o', 'two.c'])
-  end
+env(echo: :command) do |env|
+  env.Object("one.o", "one.c", 'CPPFLAGS' => ['-DONE'])
+  env.Program('two_sources.exe', ['one.o', 'two.c'])
 end

build_tests/two_sources/assuffix.rb

@@ -1,9 +1,7 @@
-default do
-  Environment.new do |env|
-    env["ASSUFFIX"] = %w[.ssss .sss]
-    env["CFLAGS"] += %w[-S]
-    env.Object("one.ssss", "one.c", "CPPFLAGS" => ["-DONE"])
-    env.Object("two.sss", "two.c")
-    env.Program("two_sources.exe", %w[one.ssss two.sss], "ASFLAGS" => env["ASFLAGS"] + %w[-x assembler])
-  end
+env do |env|
+  env["ASSUFFIX"] = %w[.ssss .sss]
+  env["CFLAGS"] += %w[-S]
+  env.Object("one.ssss", "one.c", "CPPFLAGS" => ["-DONE"])
+  env.Object("two.sss", "two.c")
+  env.Program("two_sources.exe", %w[one.ssss two.sss], "ASFLAGS" => env["ASFLAGS"] + %w[-x assembler])
 end

build_tests/two_sources/cache_strict_deps.rb

@@ -13,12 +13,10 @@ class StrictBuilder < Rscons::Builder
   end
 end
 
-default do
-  Environment.new(echo: :command) do |env|
-    env.add_builder(StrictBuilder)
-    env.Object("one.o", "one.c", "CCFLAGS" => %w[-DONE])
-    env.Object("two.o", "two.c")
-    sources = File.read("sources", mode: "rb").split(" ")
-    env.StrictBuilder("program.exe", sources)
-  end
+env(echo: :command) do |env|
+  env.add_builder(StrictBuilder)
+  env.Object("one.o", "one.c", "CCFLAGS" => %w[-DONE])
+  env.Object("two.o", "two.c")
+  sources = File.read("sources", mode: "rb").split(" ")
+  env.StrictBuilder("program.exe", sources)
 end

build_tests/two_sources/libsuffix.rb

@@ -1,8 +1,6 @@
-default do
-  Environment.new() do |env|
-    env["LIBSUFFIX"] = %w[.aaaa .aaa]
-    env.Library("one.aaaa", "one.c", "CPPFLAGS" => ["-DONE"])
-    env.Library("two.aaa", "two.c")
-    env.Program("two_sources.exe", %w[one.aaaa two.aaa])
-  end
+env do |env|
+  env["LIBSUFFIX"] = %w[.aaaa .aaa]
+  env.Library("one.aaaa", "one.c", "CPPFLAGS" => ["-DONE"])
+  env.Library("two.aaa", "two.c")
+  env.Program("two_sources.exe", %w[one.aaaa two.aaa])
 end

build_tests/two_sources/objsuffix.rb

@@ -1,8 +1,6 @@
-default do
-  Environment.new do |env|
-    env["OBJSUFFIX"] = %w[.oooo .ooo]
-    env.Object("one.oooo", "one.c", "CPPFLAGS" => ["-DONE"])
-    env.Object("two.ooo", "two.c")
-    env.Program("two_sources.exe", %w[one.oooo two.ooo])
-  end
+env do |env|
+  env["OBJSUFFIX"] = %w[.oooo .ooo]
+  env.Object("one.oooo", "one.c", "CPPFLAGS" => ["-DONE"])
+  env.Object("two.ooo", "two.c")
+  env.Program("two_sources.exe", %w[one.oooo two.ooo])
 end