Missing DW_at_low_pc information for compiled unit [AVR]
## Summary
DW_at_low_pc and DW_at_high_pc information is missing (set to zero) for a compiled unit. This complicates finding of line information in fpdebug, since it relies on this information to identify the compiled unit containing the relevant code address.
## System Information
- **Operating system:** embedded
- **Processor architecture:** AVR
- **Compiler version:** main (8abe70e25a777f8e04b5fd251d8464d5dd319200)
- **Device:** Microcontroller
Same issue is observed when using FPC 3.2.2.
## Steps to reproduce
Inspect DWARF information for any program compiled for AVR.
## Example Project
```
program test;
begin
Halt(2);
end.
```
Compile:
```
$ ~/fpc/installs/lib/fpc/3.3.1/ppcrossavr -Tembedded -Pavr -Wpavrsim -gw3 -viwn -l -al test.pp
Free Pascal Compiler version 3.3.1 [2022/06/30] for avr
Copyright (c) 1993-2022 by Florian Klaempfl and others
Target OS: Embedded
Compiling test.pp
Assembling test
Linking test
6 lines compiled, 0.1 sec, 2632 bytes code, 8535 bytes data
```
Inspect DWARF information:
```
$ avr-objdump -Wi test.elf
test.elf: file format elf32-avr
Contents of the .debug_info section:
Compilation Unit @ offset 0x0:
Length: 0x83 (32-bit)
Version: 3
Abbrev Offset: 0x0
Pointer Size: 4
<0><b>: Abbrev Number: 1 (DW_TAG_compile_unit)
<c> DW_AT_name : test.pp
<14> DW_AT_producer : Free Pascal 3.3.1 2022/06/30
<31> DW_AT_comp_dir : /home/christo/fpc/fpc-avr/src/tests/2022-07-01-unit/
<66> DW_AT_language : 9 (ANSI Pascal)
<67> DW_AT_identifier_case: 3 (case_insensitive)
<68> DW_AT_stmt_list : 0x0
<6c> DW_AT_low_pc : 0x0
<70> DW_AT_high_pc : 0x0
<1><74>: Abbrev Number: 2 (DW_TAG_subprogram)
<75> DW_AT_name : $main
<7b> DW_AT_prototyped : 1
<7c> DW_AT_external : 1
<7d> DW_AT_low_pc : 0x3a
<81> DW_AT_high_pc : 0x4e
<2><85>: Abbrev Number: 0
<1><86>: Abbrev Number: 0
```
## What is the current bug behavior?
DW_AT_low_pc and DW_AT_high_pc is 0 for the compiled unit.
## What is the expected (correct) behavior?
DW_AT_low_pc and DW_AT_high_pc should contain the lower and upper code addresses for the compiled unit.
## Speculation
Inspecting the compiler generated assembler shows that labels are defined and used seemingly correctly, but the label information is lost when the object file is created with avr-as:
```
$ avr-objdump -Wi test.o
test.o: file format elf32-avr
Contents of the .debug_info section:
Compilation Unit @ offset 0x0:
Length: 0x83 (32-bit)
Version: 3
Abbrev Offset: 0x0
Pointer Size: 4
<0><b>: Abbrev Number: 1 (DW_TAG_compile_unit)
<c> DW_AT_name : test.pp
<14> DW_AT_producer : Free Pascal 3.3.1 2022/06/30
<31> DW_AT_comp_dir : /home/christo/fpc/fpc-avr/src/tests/2022-07-01-unit/
<66> DW_AT_language : 9 (ANSI Pascal)
<67> DW_AT_identifier_case: 3 (case_insensitive)
<68> DW_AT_stmt_list : 0x0
<6c> DW_AT_low_pc : 0x0
<70> DW_AT_high_pc : 0x0
<1><74>: Abbrev Number: 2 (DW_TAG_subprogram)
<75> DW_AT_name : $main
<7b> DW_AT_prototyped : 1
<7c> DW_AT_external : 1
<7d> DW_AT_low_pc : 0x0
<81> DW_AT_high_pc : 0x14
<2><85>: Abbrev Number: 0
<1><86>: Abbrev Number: 0
```
issue