Fix integration doc about build.ninja location

[viirya]

Which issue does this PR close?

Closes #1437.

Rationale for this change

What changes are included in this PR?

Are there any user-facing changes?

[codecov-commenter]

Codecov Report

Merging #1438 (3528d21) into master (729934c) will increase coverage by 0.00%.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1438   +/-   ##
=======================================
  Coverage   82.67%   82.68%           
=======================================
  Files         185      185           
  Lines       53822    53822           
=======================================
+ Hits        44500    44502    +2     
+ Misses       9322     9320    -2     

Impacted Files	Coverage Δ
parquet/src/encodings/encoding.rs	93.52% <0.00%> (-0.20%)	⬇️
parquet_derive/src/parquet_field.rs	66.21% <0.00%> (+0.22%)	⬆️
arrow/src/datatypes/field.rs	54.10% <0.00%> (+0.30%)	⬆️
arrow/src/datatypes/datatype.rs	66.80% <0.00%> (+0.39%)	⬆️

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[alamb]

Thanks @viirya