The 22 integration tests came with a mix of removing only ROOT
(generated/OS/BUILD/MODEL) or GENERATED (generated) subdirs as
part of their `make clean`.
And running `make clean` in the druntime dir only cleaned up the
default BUILD=release variant, while running `make unittest` without
explicit BUILD type includes running the integration tests in both
debug and release variants.
Streamline/fix this to always cleaning up ROOT, and running `make clean`
in both variants when running druntime's `make clean`.
The delete operator in C++ can be called with a null pointer and
ignores it. This commit makes cpp_delete consistent with C++, so null
pointers are also ignored.
* druntime/test/*.mak: Replace -Isrc by -Iimport
* Fix Windows tests build: rt/tlsgc.d is not in import/ dir
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Co-authored-by: Denis Feklushkin <feklushkin.denis@gmail.com>
