io compartments to compression libraries

[brooksdavis]

zlib has two major parts. The core deflate compression works entierly in memory. There is also the gzlib portion which provides an analog to POSIX IO interfaces and uses IO underneath.

[brooksdavis]

With this change:

  PID COMM                 CID CNAME                                   
 1925 gzcat                  0 [RTLD]                                  
 1925 gzcat                  1 [TCB]                                   
 1925 gzcat                  2 [libunwind]                             
 1925 gzcat                  3 /usr/bin/gzcat                          
 1925 gzcat                  4 libz.so.6                               
 1925 gzcat                  5 libz.so.6:io                            
 1925 gzcat                  6 liblzma.so.5                            
 1925 gzcat                  7 libprivatezstd.so.5                     
 1925 gzcat                  8 libprivatezstd.so.5:io                  
 1925 gzcat                  9 libbz2.so.4                             
 1925 gzcat                 10 libbz2.so.4:io                          
 1925 gzcat                 11 libc.so.7:mktemp                        
 1925 gzcat                 12 libc.so.7:stdio                         
 1925 gzcat                 13 libc.so.7:mrs                           
 1925 gzcat                 14 libc.so.7:jemalloc                      
 1925 gzcat                 15 libc.so.7:string                        
 1925 gzcat                 16 libc.so.7:string.trusted                
 1925 gzcat                 17 libmd.so.7                              

liblzma appears to avoid IO entirely.

[bsdjhb]

I will pull this locally and do some testing as I want to see what the latest c18n toolchain logs for this.

[bsdjhb]

FYI, no surprises in the --verbose-c18n logs from the latest version of lld. I think this is fine to merge still.