Add a comment explaining the check for crate recompilation redundancy

ci/test-stable.sh

@@ -70,9 +70,18 @@ test-stable-bpf)
       popd
     fi
   done |& tee cargo.log
+  # Save the output of cargo building the bpf tests so we can analyze
+  # the number of redundant rebuilds of dependency crates. The
+  # expected number of solana-program crate compilations is 4. There
+  # should be 3 builds of solana-program while 128bit crate is
+  # built. These compilations are not redundant because the crate is
+  # built for different target each time. An additional compilation of
+  # solana-program is performed when simulation crate is built. This
+  # last compiled solana-program is of different version, normally the
+  # latest mainbeta release version.
   solana_program_count=$(grep -c 'solana-program v' cargo.log)
   rm -f cargo.log
-  if ((solana_program_count > 10)); then
+  if ((solana_program_count > 4)); then
       echo "Regression of build redundancy ${solana_program_count}."
       echo "Review dependency features that trigger redundant rebuilds of solana-program."
       exit 1

sdk/program/Cargo.toml

@@ -23,7 +23,7 @@ lazy_static = "1.4.0"
 log = "0.4.17"
 memoffset = "0.6"
 num-derive = "0.3"
-num-traits = "0.2"
+num-traits = { version = "0.2", default-features = true, features = ["i128", "std"] }
 rustversion = "1.0.7"
 serde = { version = "1.0", features = ["derive"] }
 serde_bytes = "0.11"