Revert "Remove a test that doesn't work yet"

This reverts commit bd65e0908f
because --gdb-index should now work with DWARF5.

test/elf/gdb-index-dwarf5.sh

@@ -0,0 +1,57 @@
+#!/bin/bash
+export LC_ALL=C
+set -e
+CC="${CC:-cc}"
+CXX="${CXX:-c++}"
+GCC="${GCC:-gcc}"
+GXX="${GXX:-g++}"
+OBJDUMP="${OBJDUMP:-objdump}"
+MACHINE="${MACHINE:-$(uname -m)}"
+testname=$(basename "$0" .sh)
+echo -n "Testing $testname ... "
+cd "$(dirname "$0")"/../..
+mold="$(pwd)/mold"
+t=out/test/elf/$testname
+mkdir -p $t
+
+[ $MACHINE = $(uname -m) ] || { echo skipped; exit; }
+
+which gdb >& /dev/null || { echo skipped; exit; }
+
+echo 'int main() {}' | $CC -o /dev/null -xc -gdwarf-5 -g - >& /dev/null ||
+  { echo skipped; exit; }
+
+cat <<EOF > $t/a.c
+#include <stdio.h>
+
+void hello() {
+  printf("Hello world\n");
+}
+
+void greet() {
+  hello();
+}
+EOF
+
+$CC -o $t/b.o -c -ggnu-pubnames -gdwarf-5 -g $t/a.c
+$CC -o $t/c.o -c -ggnu-pubnames -gdwarf-5 -g $t/a.c -gz
+
+cat <<EOF | $CC -o $t/d.o -c -xc -ggnu-pubnames -gdwarf-5 -g -
+void greet();
+
+int main() {
+  greet();
+}
+EOF
+
+$CC -B. -o $t/exe1 $t/b.o $t/d.o -Wl,--gdb-index
+$QEMU $t/exe1 | grep -q 'Hello world'
+readelf -WS $t/exe1 | fgrep -q .gdb_index
+DEBUGINFOD_URLS= gdb $t/exe1 -ex 'b main' -ex run -ex cont -ex quit >& /dev/null
+
+$CC -B. -o $t/exe2 $t/c.o $t/d.o -Wl,--gdb-index
+$QEMU $t/exe2 | grep -q 'Hello world'
+readelf -WS $t/exe2 | fgrep -q .gdb_index
+DEBUGINFOD_URLS= gdb $t/exe2 -ex 'b main' -ex run -ex cont -ex quit >& /dev/null
+
+echo OK