oe.external: move common functions here

Also provide external-common.bbclass to wrap its inclusion and setup
associated metadata. This will make easier to search sysroots for files
without pulling in the rest of the external toolchain class.

Signed-off-by: Christopher Larson <chris_larson@mentor.com>

classes/external-common.bbclass

@@ -0,0 +1,30 @@
+OE_IMPORTS += "oe.external"
+
+EXTERNAL_TOOLCHAIN_SYSROOT ?= "${@oe.external.run(d, 'gcc', *(TARGET_CC_ARCH.split() + ['-print-sysroot'])).rstrip()}"
+EXTERNAL_TOOLCHAIN_LIBROOT ?= "${@oe.external.run(d, 'gcc', *(TARGET_CC_ARCH.split() + ['-print-file-name=crtbegin.o'])).rstrip().replace('/crtbegin.o', '')}"
+
+EXTERNAL_INSTALL_SOURCE_PATHS = "\
+    ${EXTERNAL_TOOLCHAIN_SYSROOT} \
+    ${EXTERNAL_TOOLCHAIN}/${EXTERNAL_TARGET_SYS} \
+    ${EXTERNAL_TOOLCHAIN_SYSROOT}/.. \
+    ${EXTERNAL_TOOLCHAIN} \
+    ${D} \
+"
+
+# Potential locations within the external toolchain sysroot
+FILES_MIRRORS = "\
+    ${bindir}/|/usr/${baselib}/bin/\n \
+    ${base_libdir}/|/usr/${baselib}/\n \
+    ${libexecdir}/|/usr/libexec/\n \
+    ${libexecdir}/|/usr/${baselib}/${PN}\n \
+    ${mandir}/|/usr/share/man/\n \
+    ${mandir}/|/usr/man/\n \
+    ${mandir}/|/man/\n \
+    ${mandir}/|/share/doc/*-${EXTERNAL_TARGET_SYS}/man/\n \
+    ${prefix}/|${base_prefix}/\n \
+"
+
+def external_run(d, *args):
+    """Convenience wrapper"""
+    oe_import(d)
+    return oe.external.run(d, *args)