[llvm][Support] Only enable backtrace test when it's enabled

[jroelofs]

rdar://138554797

[nikic]

lld and clang already do this, so can we make it the same as they do? I.e. use ENABLE_BACKTRACE instead of LLVM_ENABLE_BACKTRACE (though really, the exported name should be renamed to have the LLVM prefix...) and name the feature backtrace? lld/clang also do the feature addition in lit.cfg.py and only assign the value from cmake in lit.site.cfg.py.in.

[jroelofs]

sure, I can make those adjustments

[nikic]

LGTM

[llvm-ci]

LLVM Buildbot has detected a new failure on builder flang-aarch64-dylib running on linaro-flang-aarch64-dylib while building llvm at step 5 "build-unified-tree".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/50/builds/9238

Here is the relevant piece of the build log for the reference

Step 5 (build-unified-tree) failure: build (failure)
...
672.090 [2042/1/4775] Building CXX object tools/mlir/lib/Dialect/MemRef/Utils/CMakeFiles/obj.MLIRMemRefUtils.dir/MemRefUtils.cpp.o
672.647 [2041/1/4776] Building CXX object tools/mlir/lib/Dialect/GPU/CMakeFiles/obj.MLIRGPUTransforms.dir/Transforms/BufferDeallocationOpInterfaceImpl.cpp.o
673.018 [2040/1/4777] Building CXX object tools/mlir/lib/Dialect/GPU/CMakeFiles/obj.MLIRGPUTransforms.dir/Transforms/DecomposeMemRefs.cpp.o
673.198 [2039/1/4778] Building CXX object tools/mlir/lib/Dialect/GPU/TransformOps/CMakeFiles/obj.MLIRGPUTransformOps.dir/Utils.cpp.o
673.395 [2038/1/4779] Building CXX object tools/mlir/lib/Dialect/Index/IR/CMakeFiles/obj.MLIRIndexDialect.dir/InferIntRangeInterfaceImpls.cpp.o
673.795 [2037/1/4780] Building CXX object tools/mlir/lib/Conversion/ArithToAMDGPU/CMakeFiles/obj.MLIRArithToAMDGPU.dir/ArithToAMDGPU.cpp.o
673.973 [2036/1/4781] Building CXX object tools/mlir/lib/Conversion/FuncToSPIRV/CMakeFiles/obj.MLIRFuncToSPIRV.dir/FuncToSPIRVPass.cpp.o
674.584 [2035/1/4782] Building CXX object tools/mlir/lib/CAPI/Conversion/CMakeFiles/obj.MLIRCAPIConversion.dir/Passes.cpp.o
674.694 [2034/1/4783] Building CXX object tools/mlir/test/lib/IR/CMakeFiles/MLIRTestIR.dir/TestPrintNesting.cpp.o
690.480 [2033/1/4784] Building CXX object tools/mlir/test/lib/IR/CMakeFiles/MLIRTestIR.dir/TestSideEffects.cpp.o
FAILED: tools/mlir/test/lib/IR/CMakeFiles/MLIRTestIR.dir/TestSideEffects.cpp.o 
/usr/local/bin/c++ -DGTEST_HAS_RTTI=0 -DMLIR_INCLUDE_TESTS -D_DEBUG -D_GLIBCXX_ASSERTIONS -D_GNU_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -I/home/tcwg-buildbot/worker/flang-aarch64-dylib/build/tools/mlir/test/lib/IR -I/home/tcwg-buildbot/worker/flang-aarch64-dylib/llvm-project/mlir/test/lib/IR -I/home/tcwg-buildbot/worker/flang-aarch64-dylib/build/tools/mlir/include -I/home/tcwg-buildbot/worker/flang-aarch64-dylib/llvm-project/mlir/include -I/home/tcwg-buildbot/worker/flang-aarch64-dylib/build/include -I/home/tcwg-buildbot/worker/flang-aarch64-dylib/llvm-project/llvm/include -I/home/tcwg-buildbot/worker/flang-aarch64-dylib/llvm-project/mlir/test/lib/IR/../Dialect/Test -I/home/tcwg-buildbot/worker/flang-aarch64-dylib/build/tools/mlir/test/lib/IR/../Dialect/Test -fPIC -fno-semantic-interposition -fvisibility-inlines-hidden -Werror=date-time -Werror=unguarded-availability-new -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wmissing-field-initializers -pedantic -Wno-long-long -Wc++98-compat-extra-semi -Wimplicit-fallthrough -Wcovered-switch-default -Wno-noexcept-type -Wnon-virtual-dtor -Wdelete-non-virtual-dtor -Wsuggest-override -Wstring-conversion -Wmisleading-indentation -Wctad-maybe-unsupported -fdiagnostics-color -ffunction-sections -fdata-sections -Wundef -Werror=mismatched-tags -O3 -DNDEBUG -std=c++17  -fno-exceptions -funwind-tables -fno-rtti -UNDEBUG -MD -MT tools/mlir/test/lib/IR/CMakeFiles/MLIRTestIR.dir/TestSideEffects.cpp.o -MF tools/mlir/test/lib/IR/CMakeFiles/MLIRTestIR.dir/TestSideEffects.cpp.o.d -o tools/mlir/test/lib/IR/CMakeFiles/MLIRTestIR.dir/TestSideEffects.cpp.o -c /home/tcwg-buildbot/worker/flang-aarch64-dylib/llvm-project/mlir/test/lib/IR/TestSideEffects.cpp
In file included from /home/tcwg-buildbot/worker/flang-aarch64-dylib/llvm-project/mlir/test/lib/IR/TestSideEffects.cpp:9:
/home/tcwg-buildbot/worker/flang-aarch64-dylib/llvm-project/mlir/test/lib/IR/../Dialect/Test/TestOps.h:148:10: fatal error: 'TestOps.h.inc' file not found
  148 | #include "TestOps.h.inc"
      |          ^~~~~~~~~~~~~~~
1 error generated.
ninja: build stopped: subcommand failed.

[ldrumm]

LGTM