dwarf: add tombstone variations (#16)

Different linkers use different values for the tombstones.

dwarf/tombstone.cpp

@@ -0,0 +1,14 @@
+// Source: https://reviews.llvm.org/D84825#2183197
+__attribute__((noinline)) void f1() { }
+void f2() {
+  int i = 3;
+  f1();
+  i = 7;
+  f1();
+}
+int main() {
+  int i = 3;
+  f1();
+  i = 7;
+  f1();
+}

dwarf/tombstone.sh

@@ -0,0 +1,10 @@
+CFLAGS="-fdebug-prefix-map=`pwd`=/object/testfiles/dwarf -ffunction-sections -Wl,-gc-sections -O3 -gdwarf-4"
+g++-13 $CFLAGS tombstone.cpp -o tombstone-loc-0 -fuse-ld=bfd
+g++-13 $CFLAGS tombstone.cpp -o tombstone-loc-addend -fuse-ld=gold
+g++-13 $CFLAGS tombstone.cpp -o tombstone-loc-1 -fuse-ld=lld -B /usr/lib/llvm-16/bin
+g++-13 $CFLAGS tombstone.cpp -o tombstone-loc-max -fuse-ld=lld -B /usr/lib/llvm-16/bin -z dead-reloc-in-nonalloc='.debug_*=0xffffffffffffffff' -z dead-reloc-in-nonalloc=.debug_loc=0xfffffffffffffffe -z dead-reloc-in-nonalloc=.debug_ranges=0xfffffffffffffffe
+
+CFLAGS="-fdebug-prefix-map=`pwd`=/object/testfiles/dwarf -ffunction-sections -Wl,-gc-sections -O3 -gdwarf-5"
+g++-13 $CFLAGS tombstone.cpp -o tombstone-loclists-0 -fuse-ld=bfd
+g++-13 $CFLAGS tombstone.cpp -o tombstone-loclists-addend -fuse-ld=gold
+g++-13 $CFLAGS tombstone.cpp -o tombstone-loclists-max -fuse-ld=lld -B /usr/lib/llvm-16/bin -z dead-reloc-in-nonalloc='.debug_*=0xffffffffffffffff' -z dead-reloc-in-nonalloc=.debug_loc=0xfffffffffffffffe -z dead-reloc-in-nonalloc=.debug_ranges=0xfffffffffffffffe