lm3s6965evb-qemu: Introduce Stellaris QEMU target

Introduces the lm3s6965evb target designed to run inside QEMU. Not all
tests have been verified on this target, but the target builds and
successfully runs some of the tests.

Change-Id: Ic0c309c691096aa18b03bd85457195d6a2b49a0b
diff --git a/pw_sys_io_baremetal_lm3s6965evb/BUILD.gn b/pw_sys_io_baremetal_lm3s6965evb/BUILD.gn
new file mode 100644
index 0000000..60828b5
--- /dev/null
+++ b/pw_sys_io_baremetal_lm3s6965evb/BUILD.gn
@@ -0,0 +1,29 @@
+# Copyright 2020 The Pigweed Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may not
+# use this file except in compliance with the License. You may obtain a copy of
+# the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations under
+# the License.
+
+import("$dir_pw_docgen/docs.gni")
+
+# This if statement allows docs to always build even if the target isn't
+# compatible with this backend.
+if (dir_pw_sys_io_backend == dir_pw_sys_io_baremetal_lm3s6965evb) {
+  source_set("pw_sys_io_baremetal_lm3s6965evb") {
+    public_deps = [ "$dir_pw_boot_armv7m" ]
+    deps = [
+      "$dir_pw_preprocessor",
+      "$dir_pw_sys_io:default_putget_bytes",
+      "$dir_pw_sys_io:facade",
+    ]
+    sources = [ "sys_io_baremetal.cc" ]
+  }
+}