docs: fix go tool nm usage in binary-size.md

[kolyshkin]

What type of PR is this?

• documentation

What this PR does / why we need it:

The binary size doc ran go tool nm on a binary built with -ldflags="-s -w",
which has no symbol table, so nm only reports no symbols.

Also, piping the output to sort -nr sorts by the first column, which is the
symbol address (in hex), not the size.

Run nm on a binary built without -s -w, and use its own -sort size option.

Which issue(s) this PR fixes:

None (fixes 679f715, "Document v3 binary size checks").

Testing

Checked with a hello-world binary: stripped one gives no symbol section /
no symbols; go tool nm -size -sort size lists the largest symbols first,
while | sort -nr orders them by address.

Release Notes

NONE

[greptile-apps]

Confidence Score: 5/5

[Low risk] Fixes documentation about binary inspection tools.

The documentation change appears safe to merge.

Summary

The documentation now rebuilds the binary with symbols before inspecting it and asks go tool nm to sort symbols by size.

_{Reviews (1) · Last reviewed commit: "docs: fix go tool nm usage in binary-siz..."}

[coilysiren]

@kolyshkin can you should me a before and after of the command output?

[kolyshkin]

Please try it yourself -- all you need is Go installed.

Basically, "before" doesn't work because the binary is stripped, and even when it's not, the output is sorted by address (rather than size).

After is what the original author had in mind (I guess).

[coilysiren]

😅 the purpose of the ask is to provide documentation, not for me to see the diff personally

Here's a format for you

---

before

# input
ls "~/camels"| rg water | xargs drink.sh

# output
wow I love this, but it wasnt much

after

# input
ls "~/camels" | rg liquid | xargs drink.sh

# output
this was okay, and I feel satisfied