[gdb/testsuite] Fix .debug_aranges in dw2-case-insensitive-debug.S

When running gdb.dwarf2/dw2-case-insensitive.exp with target board
cc-with-debug-names, we run into:
...
FAIL: gdb.dwarf2/dw2-case-insensitive.exp: regexp case-sensitive off \
  (GDB internal error)
...
in more detail:
...
(gdb) info functions fUnC_lang
gdb/dwarf2read.c:5293: internal-error: \
  compunit_symtab* dw2_find_pc_sect_compunit_symtab(objfile*, \
  bound_minimal_symbol, CORE_ADDR, obj_section*, int): \
  Assertion `result != NULL' failed.
...

The problem is that the .debug_aranges section in dw2-case-insensitive-debug.S
contains a debug_info_offset which is set to 0:
...
        .section        .debug_aranges,"",@progbits
        .4byte  .Laranges_end - .Laranges_start
.Laranges_start:
        .2byte  0x2
        .4byte  0
...
while the compilation unit at offset 0 in the .debug_section of the executable
is in fact not the compilation unit generated from
dw2-case-insensitive-debug.S.

This happens when linked in object files contain dwarf info and are placed in
the .debug_info section before the compilation unit generated from
dw2-case-insensitive-debug.S.

Fix this by defining the debug_info_offset field using the label .Lcu1_begin
that defines the start of the compilation unit:
...
-       .4byte  0
+       .4byte  .Lcu1_begin
...

Tested on x86_64-linux with native, cc-with-gdb-index and cc-with-debug-names.

gdb/testsuite/ChangeLog:

2019-05-07  Tom de Vries  <tdevries@suse.de>

	PR testsuite/24522
	* gdb.dwarf2/dw2-case-insensitive-debug.S: Fix debug_info_offset in
	.debug_aranges section.

2 files changed, 7 insertions, 1 deletions

diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index e2b5075..c514c03 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,5 +1,11 @@
 2019-05-07  Tom de Vries  <tdevries@suse.de>
 
+	PR testsuite/24522
+	* gdb.dwarf2/dw2-case-insensitive-debug.S: Fix debug_info_offset in
+	.debug_aranges section.
+
+2019-05-07  Tom de Vries  <tdevries@suse.de>
+
 	PR testsuite/24159
 	* lib/dwarf.exp: Fix handling of DW_FORM_ref_addr.
 
diff --git a/gdb/testsuite/gdb.dwarf2/dw2-case-insensitive-debug.S b/gdb/testsuite/gdb.dwarf2/dw2-case-insensitive-debug.S
index f12a821..7f5e1a5 100644
--- a/gdb/testsuite/gdb.dwarf2/dw2-case-insensitive-debug.S
+++ b/gdb/testsuite/gdb.dwarf2/dw2-case-insensitive-debug.S
@@ -64,7 +64,7 @@
 	.4byte	.Laranges_end - .Laranges_start	// Length of Address Ranges Info
 .Laranges_start:
 	.2byte	0x2	// DWARF Version
-	.4byte	0 // .Ldebug_info0 - Offset of Compilation Unit Info
+	.4byte	.Lcu1_begin // .Ldebug_info0 - Offset of Compilation Unit Info
 	.byte	PTRBITS / 8	// Size of Address
 	.byte	0	// Size of Segment Descriptor
 	.2byte	0	// Pad to 16 byte boundary