Restrict memory-analyzer build to Linux x86_64/i386

[tautschnig]

We do not currently have an implementation of calling conventions for any other platform.

Fixes: #7934

• Each commit message has a non-empty body, explaining why the change was made.
• n/a Methods or procedures I have added are documented, following the guidelines provided in CODING_STANDARD.md.
• n/a The feature or user visible behaviour I have added or modified has been documented in the User Guide in doc/cprover-manual/
• Regression or unit tests are included, or existing tests cover the modified code (in this case I have detailed which ones those are in the commit message).
• n/a My commit message includes data points confirming performance improvements (if claimed).
• My PR is restricted to a single feature or bugfix.
• n/a White-space or formatting changes outside the feature-related changed lines are in commits of their own.

[codecov]

Codecov Report

All modified lines are covered by tests ✅

Comparison is base (a531056) 78.75% compared to head (a738f6d) 78.83%.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #7958      +/-   ##
===========================================
+ Coverage    78.75%   78.83%   +0.07%     
===========================================
  Files         1701     1701              
  Lines       196224   196224              
===========================================
+ Hits        154540   154694     +154     
+ Misses       41684    41530     -154     

see 35 files with indirect coverage changes

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[esteffin]

This condition means that memory analyzer will be built on Mac with Intel.
Is this the intended behaviour?

[tautschnig]

No, that would not fulfil CMAKE_SYSTEM_NAME STREQUAL Linux.