Test DWARFv5 with gdb-index and low_pc/high_pc on the CU (rather than ranges)

There was a bug in LLVM's libDebugInfo where it did not porpagate the
section index through the range query built from low_pc/high_pc. Hard to
test in LLVM, so I'm adding a test here.

llvm-svn: 350011

lld/test/ELF/gdb-index-dwarf5-low-high.s

@@ -0,0 +1,50 @@
+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
+# RUN: ld.lld --gdb-index %t.o -o %t
+# RUN: llvm-dwarfdump -gdb-index %t | FileCheck %s
+
+# CHECK:       Address area offset = 0x28, has 1 entries:
+# CHECK-NEXT:    Low/High address = [0x201000, 0x201001) (Size: 0x1), CU id = 0
+
+	.text
+	.globl main
+main:                                   # @main
+.Lfunc_begin0:
+	retq
+.Lfunc_end0:
+	.section	.debug_abbrev,"",@progbits
+	.byte	1                       # Abbreviation Code
+	.byte	17                      # DW_TAG_compile_unit
+	.byte	0                       # DW_CHILDREN_no
+	.byte	115                     # DW_AT_addr_base
+	.byte	23                      # DW_FORM_sec_offset
+	.byte	17                      # DW_AT_low_pc
+	.byte	27                      # DW_FORM_addrx
+	.byte	18                      # DW_AT_high_pc
+	.byte	6                       # DW_FORM_data4
+	.byte	0                       # EOM(1)
+	.byte	0                       # EOM(2)
+	.byte	0                       # EOM(3)
+	.section	.debug_info,"",@progbits
+.Lcu_begin0:
+	.long	.Ldebug_info_end0-.Ldebug_info_start0 # Length of Unit
+.Ldebug_info_start0:
+	.short	5                       # DWARF version number
+	.byte	1                       # DWARF Unit Type
+	.byte	8                       # Address Size (in bytes)
+	.long	.debug_abbrev           # Offset Into Abbrev. Section
+	.byte	1                       # Abbrev [1] 0xc:0x2b DW_TAG_compile_unit
+	.long	.Laddr_table_base0      # DW_AT_addr_base
+	.byte	0                       # DW_AT_low_pc
+	.long	.Lfunc_end0-.Lfunc_begin0 # DW_AT_high_pc
+.Ldebug_info_end0:
+	.section	.debug_macinfo,"",@progbits
+	.byte	0                       # End Of Macro List Mark
+	.section	.debug_addr,"",@progbits
+	.long	12
+	.short	5
+	.byte	8
+	.byte	0
+.Laddr_table_base0:
+	.quad	.Lfunc_begin0
+