[LSan] Disable backtracing for the lsan builds.

We don't need or want it there, and it's causing dependency problems in
our CMake build system.

rdar://110420951

Author: al45tair

utils/build-presets.ini

@@ -1223,6 +1223,8 @@ sourcekit-lsp=0
 [preset: buildbot_incremental_linux,lsan,tools=RDA,stdlib=RDA,test=no]
 build-subdir=buildbot_incremental_lsan
 
+swift-enable-backtracing=0
+
 # Reduce the size of the final toolchain, limit debug info
 extra-cmake-options=
    -DCMAKE_C_FLAGS="-gline-tables-only"
@@ -1238,6 +1240,8 @@ reconfigure
 [preset: buildbot_incremental_linux,lsan,tools=RDA,stdlib=DA,test=no]
 build-subdir=buildbot_incremental_lsan
 
+swift-enable-backtracing=0
+
 # Reduce the size of the final toolchain, limit debug info
 extra-cmake-options=
    -DCMAKE_C_FLAGS="-gline-tables-only"