build: check golang version meets min req.

Check that the system golang version is new enough to build with
according to the data from the `versions.yaml` file.

Update the verions in the versions.yaml accordingly, and add a note
describing what the 'newest-version' item represents.
Note, we only do a minimum requirement check, and are not checking
against the 'newest-version' info from the yaml.

Fixes: #148

Inspired-by: Wei Zhang <zhangwei555@huawei.com>
Idea-by: James O. D. Hunt <james.o.hunt@intel.com>
Signed-off-by: Graham Whaley <graham.whaley@intel.com>

Makefile

@@ -15,6 +15,8 @@ done)
 GOARCH=$(shell go env GOARCH)
 HOST_ARCH=$(shell arch)
 
+include golang.mk
+
 ifeq ($(ARCH),)
 	ARCH = $(GOARCH)
 endif

golang.mk

@@ -0,0 +1,46 @@
+#
+# Copyright (c) 2018 Intel Corporation
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+# Check that the system golang version is within the required version range
+# for this project.
+
+golang_version_min=$(shell yq r versions.yaml languages.golang.version)
+
+ifeq (,$(golang_version_min))
+    $(error "ERROR: cannot determine minimum golang version")
+endif
+
+golang_version_min_fields=$(subst ., ,$(golang_version_min))
+
+golang_version_min_major=$(word 1,$(golang_version_min_fields))
+golang_version_min_minor=$(word 2,$(golang_version_min_fields))
+
+# for error messages
+golang_version_needed=$(golang_version_min_major).$(golang_version_min_minor)
+
+golang_version_raw=$(shell go version 2>/dev/null)
+
+ifeq (,$(golang_version_raw))
+    $(error "ERROR: cannot determine golang version")
+endif
+
+# determine actual version of golang
+golang_version=$(subst go,,$(word 3,$(golang_version_raw)))
+
+golang_version_fields=$(subst ., ,$(golang_version))
+
+golang_version_major=$(word 1,$(golang_version_fields))
+golang_version_minor=$(word 2,$(golang_version_fields))
+
+golang_major_ok=$(shell test $(golang_version_major) -ge $(golang_version_min_major) && echo ok)
+golang_minor_ok=$(shell test $(golang_version_major) -eq $(golang_version_min_major) -a $(golang_version_minor) -ge $(golang_version_min_minor) && echo ok)
+
+ifeq (,$(golang_major_ok))
+    $(error "ERROR: golang major version too old: got $(golang_version), need atleast $(golang_version_needed)")
+endif
+
+ifeq (,$(golang_minor_ok))
+    $(error "ERROR: golang minor version too old: got $(golang_version), need atleast $(golang_version_needed)")
+endif

versions.yaml

@@ -189,7 +189,10 @@ languages:
     issue: "https://github.com/golang/go/issues/20676"
     version: "1.10.4"
     meta:
-      newest-version: "1.11"
+      description: |
+        'newest-version' is the latest version known to work when
+        building Kata
+      newest-version: "1.11.1"
 
 specs:
   description: "Details of important specifications"