Allow atblgen to process sequence_order.in with empty lines in between lines for building on Macos

[AngheloAlf]

This fixes building on macos due to a kinda specific issue with Apple clang.

The issue

When trying to build on Macos (specifically MacOS 12, Monteray with Apple clang 13.0.0 (clang-1300.0.29.30), idk if other versions have this issue too) make stops with the following error from atblgen:

Failed to match line 1: ""
regexec error: "regexec() failed to match"
Error: Malformed build/n64-us/assets/audio/sequence_order.in?

atblgen makes the assumption that the sequence_order.in file has no extra data, spaces, empty lines, etc. but the file somehow ends up having empty lines between each line on macos.

This file is created by using the C preprocessor to process include/tables/sequence_table.h.
In normal circumstances this file should look like this snip,

(Sequence_0,NA_BGM_GENERAL_SFX)
(Sequence_1,NA_BGM_AMBIENCE)
(Sequence_2,NA_BGM_TERMINA_FIELD)
(Sequence_3,NA_BGM_CHASE)
(Sequence_4,NA_BGM_MAJORAS_THEME)

but it ends up looking like this instead

(Sequence_0,NA_BGM_GENERAL_SFX)

(Sequence_1,NA_BGM_AMBIENCE)

(Sequence_2,NA_BGM_TERMINA_FIELD)

(Sequence_3,NA_BGM_CHASE)

(Sequence_4,NA_BGM_MAJORAS_THEME)

which atblgen doesn't like.

I believe this happens because there are lines with comments between each macro in sequence_table.h and for some reason this Apple clang version decided to preserve those empty lines

The fix

The fix just makes atblgen skip empty lines.

Misc

I threw atblgen to valgrind to check the fix was working as intended and noted a bunch of memory leaks, so I fixed them.

I also noted the tools/audio makefile was not using OPTFLAGS when building those tools, so I fixed that too.

[Thar0]

Do you mind adding skipping initial whitespace up to the first non-empty line as well? The behavior right now would miss initial whitespace but handle all other cases properly, might as well cover all cases of extra empty lines?

[Thar0]

On this, I wouldn't strictly call this a memory leak, the program is about to exit. I didn't bother cleaning up the memory for that reason, but since you've added it now it's not a big deal to keep it