libcamera: backtrace: Include cxxabi.h without HAVE_DW

Since it's used in code without HAVE_DW, it fails to compile on such
systems e.g. linux/musl

Fixes
src/libcamera/base/backtrace.cpp:235:16: error: use of undeclared identifier 'abi'
                char *name = abi::__cxa_demangle(symbol, nullptr, nullptr, nullptr);
                             ^
1 error generated.

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

src/libcamera/base/backtrace.cpp

@@ -13,7 +13,6 @@
 #endif
 
 #ifdef HAVE_DW
-#include <cxxabi.h>
 #include <elfutils/libdwfl.h>
 #include <unistd.h>
 #endif
@@ -27,6 +26,7 @@
 #include <libunwind.h>
 #endif
 
+#include <cxxabi.h>
 #include <sstream>
 
 #include <libcamera/base/span.h>