You can override the compression algorithm used by the linker by either:

To specify a compression algorithm, use the number of the required compressor on the linker command line, for example:

armlink --datacompressor 2 ... 

Use the command-line option --datacompressor list to get a list of compression algorithms available in the linker:

armlink --datacompressor list
...
Num	Compression algorithm
========================================================
0	Run-length encoding
1	Run-length encoding, with LZ77 on small-repeats
2	Complex LZ77 compression

When choosing a compression algorithm be aware that:

The linker prefers compressor 0 or 1 where the data contains mostly zero-bytes (>75%). Compressor 2 is chosen where the data contains few zero-bytes (<10%). If the image is made up only of ARM code, then ARM decompressors are used automatically. If the image contains any Thumb code, Thumb decompressors are used. If there is no clear preference, all compressors are tested to produce the best overall size.