darwintracelib1.0: Fix tests

Invoking [setup] enables the tracing sandbox, which means that binaries
started after that must be started via system or must not be arm64e
system binaries (which are untraceable unmodified and will crash with
DYLD_INSERT_LIBRARIES set).

The reverse applies for [expect] in the cleanup phase.

Use system for invocations of system utilities that should be traced
when invoked after [setup]. Move invocations that don't need to be
traced after [expect] in cleanup.

Add infrastructure required to use system (e.g., allow access to the
shell and provide `ui_info` and `ui_debug`).

src/darwintracelib1.0/tests/darwintrace.test

@@ -128,9 +128,8 @@ test darwintrace_relative_symlinks "Test that resolution of relative symlinks wo
         set levels [llength [regexp -all -inline -- "/" $cwd]]
         set path "[string repeat "../" [expr {$levels + 2}]]$cwd//./stat"
 
-        [setup [list allow "$cwd/symlink"]]
-
-        exec -ignorestderr -- ln -s $path symlink
+        [setup [list allow "$cwd/symlink" allow "/private/var/select/sh" allow "/bin" allow $env(DARWINTRACE_SIP_WORKAROUND_PATH)]]
+        system "/bin/ln -s $path symlink"
     } \
     -cleanup {
         file delete -force symlink
@@ -142,7 +141,7 @@ test darwintrace_relative_symlinks "Test that resolution of relative symlinks wo
 test darwintrace_long_symlinks "Test that resolution of long symlinks does not trigger the stack canary" \
     -setup {
         [setup [list allow /]]
-        exec -- ln -s [string repeat "ab/de/ghi/" 102] longlink
+        system "/bin/ln -s [string repeat "ab/de/ghi/" 102] longlink"
     } \
     -cleanup {
         [expect]

src/darwintracelib1.0/tests/readdir.test

@@ -50,8 +50,8 @@ test darwintrace_readdir_at_maxpathlen "Test that readdir(3) with a directory at
         [setup [list allow $cwd]]
     } \
     -cleanup {
-        exec -ignorestderr -- rm -rf ab
         [expect]
+        exec -ignorestderr -- rm -rf ab
     } \
     -body {
         set lines [split [exec -ignorestderr -- ./readdir $dirname 2>@1] "\n"]

src/darwintracelib1.0/tests/testlib.tcl

@@ -186,3 +186,10 @@ proc tracelib_cleanup {} {
     array unset env DARWINTRACE_LOG
 }
 
+# used by the 'system' builtin in Pextlib.dylib
+proc ui_info {msg} {
+    puts stderr "$msg"
+}
+proc ui_debug {msg} {
+    puts stderr "$msg"
+}