Refactor common makefile fragments
In preparation for setting up another Kati stage, move some common
settings and tools into a common folder. This way it's a bit easier to
see that they're safe to use, and that they shouldn't depend on anything
outside of the common folder.
Bug: 117463001
Test: build-aosp_arm.ninja is the same before and after
Change-Id: Ief4b75a4dbe45b73ffd03bf32c60695c816d979d
diff --git a/common/core.mk b/common/core.mk
new file mode 100644
index 0000000..e5264b0
--- /dev/null
+++ b/common/core.mk
@@ -0,0 +1,56 @@
+#
+# Copyright (C) 2018 The Android Open Source Project
+#
+# 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
+#
+# http://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.
+#
+
+# Only use ANDROID_BUILD_SHELL to wrap around bash.
+# DO NOT use other shells such as zsh.
+ifdef ANDROID_BUILD_SHELL
+SHELL := $(ANDROID_BUILD_SHELL)
+else
+# Use bash, not whatever shell somebody has installed as /bin/sh
+# This is repeated from main.mk, since envsetup.sh runs this file
+# directly.
+SHELL := /bin/bash
+endif
+
+# Utility variables.
+empty :=
+space := $(empty) $(empty)
+comma := ,
+# Note that make will eat the newline just before endef.
+define newline
+
+
+endef
+# The pound character "#"
+define pound
+#
+endef
+# Unfortunately you can't simply define backslash as \ or \\.
+backslash := \a
+backslash := $(patsubst %a,%,$(backslash))
+
+# Prevent accidentally changing these variables
+.KATI_READONLY := SHELL empty space comma newline pound backslash
+
+# Basic warning/error wrappers. These will be redefined to include the local
+# module information when reading Android.mk files.
+define pretty-warning
+$(warning $(1))
+endef
+
+define pretty-error
+$(error $(1))
+endef