gas: add Dwarf line number test for .macro expansions

Before fiddling with the code let's put in place a test covering what
PR/gas 16908 aimed at.

gas/testsuite/gas/elf/dwarf-5-macro.d

@@ -0,0 +1,27 @@
+#as: --gdwarf-5
+#name: line number entries for .macro expansions
+#readelf: -W -wl
+# The am33 cr16 crx ft32 mn10* msp430 nds32* and rl78 targets do not evaluate the subtraction of symbols at assembly time.
+# The d30v target emits sufficiently different debug info, apparently also covering padding it inserts.
+# The riscv targets do not support the subtraction of symbols.
+#xfail: am33*-* cr16-* crx-* d30v-* ft32-* mn10*-* msp430-* nds32*-* riscv*-* rl78-*
+
+Raw dump of debug contents .*
+#...
+ Line Number Statements:
+.*Extended opcode 2: .*
+.*Advance Line by 10017 to 10018
+.*(Copy|Special opcode .* Address by 0 .* and Line by 0 to 10018)
+.*Special opcode .* and Line by 1 to 10019
+.*Special opcode .* and Line by 1 to 10020
+.*Set File Name to entry 2 .*
+.*Advance Line by -10012 to 8
+.*Special opcode .* and Line by 0 to 8
+.*Set File Name to entry 1 .*
+.*Advance Line by 10018 to 10026
+.*(Advance PC by .*|Special opcode .* and Line by 0 to 10026)
+#...
+.*Special opcode .* and Line by 1 to 10027
+.*Special opcode .* and Line by 1 to 10028
+.*Advance PC by .*
+.*Extended opcode 1: End of Sequence

gas/testsuite/gas/elf/dwarf-5-macro.s

@@ -0,0 +1,28 @@
+	.macro m1 args:vararg
+	.nop
+	.endm
+
+	.macro m2 args:vararg
+	.file "Line.s"
+	.line 7
+	.nop
+	.endm
+
+	.macro m3 args:vararg
+# 10013 "line.S"
+	.nop
+	.endm
+
+	.text
+macro:
+	m1 1
+	m1 2
+	m1 3
+
+	m2 1
+	m2 2
+	m2 3
+
+	m3 1
+	m3 2
+	m3 3

gas/testsuite/gas/elf/elf.exp

@@ -308,6 +308,7 @@ if { [is_elf_format] } then {
     run_dump_test "dwarf-5-cu" $dump_opts
     run_dump_test "dwarf-5-nop-for-line-table" $dump_opts
     run_dump_test "dwarf-5-irp" $dump_opts
+    run_dump_test "dwarf-5-macro" $dump_opts
     run_dump_test "dwarf-3-func" $dump_opts
     run_dump_test "dwarf-5-func" $dump_opts
     run_dump_test "dwarf-5-func-global" $dump_opts