Instruct users to install APRON from source (#78).

The version of APRON provided by some distributions includes a bug that
was fixed in more recent versions.

This commit includes a new entry in the TROUBLESHOOTING document to
point users to the new repo, and instruct them to build APRON from
source.

[ci skip]

TROUBLESHOOTING.md

@@ -63,6 +63,10 @@ Your LLVM library was built as one single shared library `libLLVM.so` (`LLVM_BUI
 
 Compiling IKOS with both `-DBUILD_SHARED_LIBS=ON` and `-DIKOS_LINK_LLVM_DYLIB=ON` should fix the issue by linking against the single libLLVM shared library.
 
+### `memory access violation at address: 0x00000088: no mapping at fault address` while running tests
+
+This is a bug in the APRON library. Some distributions provide an older version of APRON that includes a bug, but that bug was fixed upstream. Make sure you build APRON from source (https://github.com/antoinemine/apron), instead of relying on a version made available via your distribution's package repository.
+
 Analysis issues
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