toolchain-scripts.bbclass: use double quotes for exported PS1
Use double quotes("") rather than single quotes('') for PS1 in
EXPORT_SDK_PS1 which will be exported in SDK environment file. Then it
could set PS1 for SDK env with some variables in host env, such as the
original PS1. The SDK PS1 could be some distinct words plus original PS1
rather than replace the whole original PS1. For example, it could set in
local.conf with
SDK_PS1 = "(oesdk) \${PS1}"
then it just prepends '(oesdk) ' before original PS1 after source the
SDK environment file.
Signed-off-by: Kai Kang <kai.kang@windriver.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
