convert Object builder specs to integration tests

build_tests/simple/error_unknown_suffix.rb

@@ -0,0 +1,6 @@
+Rscons::Environment.new do |env|
+  File.open("foo.xyz", "wb") do |fh|
+    fh.puts("hi")
+  end
+  env.Object("foo.o", "foo.xyz")
+end

build_tests/simple/override_cccmd.rb

@@ -0,0 +1,4 @@
+Rscons::Environment.new(echo: :command) do |env|
+  env.Object("simple.o", "simple.c",
+             "CCCMD" => %w[${CC} -c -o ${_TARGET} -Dfoobar ${_SOURCES}])
+end

build_tests/simple/override_depfilesuffix.rb

@@ -0,0 +1,4 @@
+Rscons::Environment.new(echo: :command) do |env|
+  env["DEPFILESUFFIX"] = ".deppy"
+  env.Object("simple.o", "simple.c")
+end