cmake build system: change default build type to `Release` (#36679)

This switches the default Make build type to `build_type=Release`.

This offers:
- higher optimization level, including loop vectorization on older GCC
- adds NDEBUG define, which disables assertions, which could cause speedups if assertions are in loops etc
- no `-g` means smaller install size

Downsides are:
- worse backtraces (though this does NOT strip symbols)
- perf reports may be useless
- no function arguments / local variables in debugger (could be of course)
- no file path / line numbers in debugger

The downsides can be mitigated by overriding to `build_type=RelWithDebInfo` in `packages.yaml`,
if needed.  The upside is that builds will be MUCH smaller (and faster) with this change.

---------

Co-authored-by: Gregory Becker <becker33@llnl.gov>

1 files changed, 0 insertions, 6 deletions

diff --git a/var/spack/repos/builtin/packages/llvm/package.py b/var/spack/repos/builtin/packages/llvm/package.py
index c7cc2df3c8..f62822e3ca 100644
--- a/var/spack/repos/builtin/packages/llvm/package.py
+++ b/var/spack/repos/builtin/packages/llvm/package.py
@@ -162,12 +162,6 @@ class Llvm(CMakePackage, CudaPackage):
         multi=True,
     )
     variant(
-        "build_type",
-        default="Release",
-        description="CMake build type",
-        values=("Debug", "Release", "RelWithDebInfo", "MinSizeRel"),
-    )
-    variant(
         "omp_tsan",
         default=False,
         when="@6:",