in the liteos_a directory, we used to use `make clean all` command
to build liteos_a kernel for test.
Signed-off-by: NCaoruihong <crh.cao@huawei.com>
Change-Id: I5ca689c1c44052f7de937d7faa9e4d3534d97380

sysroot and arch related cflags are pass by BUILD.gn now.
Signed-off-by: NCaoruihong <crh.cao@huawei.com>
Change-Id: Ia6000dd7ed8a8a37e935ace49d8460a919a16566

clang不支持“-flto,-Oz”作为链接选项，但是可以作为编译选项，且作为编译选项时，有更好的size减少效果。这里为了使用这种
编译选项组合，且为了不影响链接过程（Build.sh链接时也会使用CFLAGS），在链接选项生效的-O选项中，重置其为O2。
最终size可以从300+k,缩减为不到180k。

Close #I3UVEV

Change-Id: If29ac4a058bcd40c4c36deb484c9468c93bcd1ec
Signed-off-by: NGuangyao Ma <guangyao.ma@outlook.com>

Change-Id: I73055c0d9b9ceb27adb687089be4d332ec323b9c

Change-Id: I0a6e6f2962ca6904c858898eb93a5b2f93e85b69

Change-Id: I052d930d54e63179b17b77f02c107a015f3cfc3f

Change-Id: Ia6c1f6302407a707b3ec9b805f4c92d8a7970b86