Testsuite: Add option to build & install TGen_RTS from source

This reduces manual work in development setups, and can help to
avoid potential race conditions if a non-externally built version of
TGen_RTS is present in the GPR_PROJECT_PATH env var

testsuite/testsuite.py

@@ -12,7 +12,6 @@
 
 import e3.testsuite
 from e3.fs import sync_tree
-from e3.os.fs import which
 from e3.os.process import Run
 
 from drivers.python_script import PythonScriptDriver
@@ -46,6 +45,13 @@ def add_options(self, parser):
             action="store_true",
             help="Rewrite test baselines according to current output.",
         )
+        parser.add_argument(
+            "--setup-tgen-rts",
+            action="store_true",
+            help="Build and install TGen_RTS to prevent tests from re-building"
+                 " the library. This is not needed if the environment already"
+                 " provides the installed project."
+        )
 
     def set_up(self):
         super().set_up()
@@ -67,6 +73,45 @@ def set_up(self):
             os.environ["PATH"],
         )
 
+        if self.main.args.setup_tgen_rts:
+            # Copy the TGen_RTS sources from the tree to a temporary directory
+            rts_build_dir = os.path.join(self.working_dir, "tgen_rts")
+            rts_install_dir = os.path.join(rts_build_dir, "local")
+            sync_tree(
+                os.path.join(self.root_dir, "..", "src", "tgen", "tgen_rts"),
+                rts_build_dir
+            )
+            e3.testsuite.logger.info("Building TGen_RTS ...")
+            p_build = Run([
+                "gprbuild",
+                f"-P{os.path.join(rts_build_dir, 'tgen_rts.gpr')}",
+                "-g",
+                "-bargs",
+                "-Es"
+            ])
+            if p_build.status != 0:
+                e3.testsuite.logger.fatal(
+                    f"Failed to build TGen_RTS: {p_build.out}"
+                )
+                exit(1)
+
+            e3.testsuite.logger.info("Installing TGen_RTS ...")
+            p_install = Run([
+                "gprinstall",
+                "-p",
+                f"-P{os.path.join(rts_build_dir, 'tgen_rts.gpr')}",
+                f"--prefix={rts_install_dir}",
+            ])
+            if p_install.status != 0:
+                e3.testsuite.logger.fatal(
+                    f"Failed to install TGen_RTS: {p_install.out}"
+                )
+                exit(1)
+            self.env.add_search_path(
+                "GPR_PROJECT_PATH",
+                os.path.join(rts_install_dir, "share", "gpr")
+            )
+
         if self.env.valgrind:
             # The --valgrind switch was given. Set the PATH to point to the
             # valgrind directory (see ../../valgrind/README).