[continuous-integration] add POSIX SPI build (#4913)

This adds a CI build for POSIX platform with SPI enabled.

Also fixed a build error in `spi_interface.cpp`.

script/check-posix-build

@@ -32,6 +32,7 @@ set -euxo pipefail
 main()
 {
     "$(dirname "$0")"/check-posix-build-autotools
+    "$(dirname "$0")"/check-posix-build-cmake
 }
 
 main "$@"

script/check-posix-build-autotools

@@ -41,8 +41,10 @@ build()
     reset_source
     make -f src/posix/Makefile-posix
 
-    reset_source
-    make -f src/posix/Makefile-posix RCP_SP=1
+    if [[ $OSTYPE != "darwin"* ]] ; then
+        reset_source
+        make -f src/posix/Makefile-posix RCP_BUS=spi
+    fi
 }
 
 main()

script/check-posix-build-cmake

@@ -0,0 +1,69 @@
+#!/bin/bash
+#
+#  Copyright (c) 2020, The OpenThread Authors.
+#  All rights reserved.
+#
+#  Redistribution and use in source and binary forms, with or without
+#  modification, are permitted provided that the following conditions are met:
+#  1. Redistributions of source code must retain the above copyright
+#     notice, this list of conditions and the following disclaimer.
+#  2. Redistributions in binary form must reproduce the above copyright
+#     notice, this list of conditions and the following disclaimer in the
+#     documentation and/or other materials provided with the distribution.
+#  3. Neither the name of the copyright holder nor the
+#     names of its contributors may be used to endorse or promote products
+#     derived from this software without specific prior written permission.
+#
+#  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+#  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+#  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+#  ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+#  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+#  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+#  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+#  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+#  CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+#  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+#  POSSIBILITY OF SUCH DAMAGE.
+#
+
+set -euxo pipefail
+
+readonly OT_BUILDDIR="$(pwd)/build"
+readonly OT_SRCDIR="$(pwd)"
+
+reset_source()
+{
+    git checkout -- .
+    git clean -xfd
+}
+
+build()
+{
+    local options=("$@")
+
+    options+=(
+        "-DOT_COMPILE_WARNING_AS_ERROR=on"
+        "-DOT_PLATFORM=posix"
+    )
+
+    mkdir -p $OT_BUILDDIR
+    cd $OT_BUILDDIR
+    cmake -GNinja "${options[@]}" $OT_SRCDIR
+    ninja
+
+    cd $OT_SRCDIR
+}
+
+main()
+{
+    reset_source
+    build
+
+    if [[ $OSTYPE != "darwin"* ]] ; then
+        reset_source
+        build -DOT_POSIX_CONFIG_RCP_BUS=SPI
+    fi
+}
+
+main "$@"