[clang] [test] Disable the test exhausting stack on NetBSD

[mgorny]

Summary

Disable the instantiation-depth-default.cpp test on NetBSD since it
requires more stack space than we have by default on NetBSD.

[phosek]

LGTM

clang/test/SemaTemplate/instantiation-depth-default.cpp

 // RUN: %clang_cc1 -fsyntax-only -verify -ftemplate-backtrace-limit 2 %s
 //
 // FIXME: Disable this test when Clang was built with ASan, because ASan
 // increases our per-frame stack usage enough that this test no longer fits
 // within our normal stack space allocation.
 // UNSUPPORTED: asan
+//
+// The default stack size on NetBSD is too small for this test.
+// UNSUPPORTED: system-netbsd
 
 template<int N, typename T> struct X : X<N+1, T*> {};
 // expected-error-re@8 {{recursive template instantiation exceeded maximum depth of 1024{{$}}}}
 // expected-note@8 {{instantiation of template class}}
 // expected-note@8 {{skipping 1023 contexts in backtrace}}
 // expected-note@8 {{use -ftemplate-depth=N to increase recursive template instantiation depth}}
 
 X<0, int> x; // expected-note {{in instantiation of}}
 
 // FIXME: It crashes. Investigating.
 // UNSUPPORTED: windows-gnu