Build spawn-helper in its own project

* So it can be added to TRUFFLERUBY_BOOTSTRAP_HOME.
* It is notably used for `system`/`spawn`/etc with `chdir:`,
  which is used e.g. in src/main/c/psych/extconf.rb.

Author: eregon

mx.truffleruby/suite.py

@@ -238,6 +238,13 @@
             },
         },
 
+        "org.truffleruby.spawnhelper": {
+            "dir": "src/main/c/spawn-helper",
+            "native": "executable",
+            "deliverable": "spawn-helper",
+            "cflags": ["-g", "-O3", "-std=c99", "-Wall", "-Werror"],
+        },
+
         "org.prism.libprism": {
             "class": "YARPNativeProject",
             "dir": "src/main/c/yarp",
@@ -422,7 +429,6 @@
             },
             "output": ".",
             "results": [
-                "src/main/c/spawn-helper/spawn-helper",
                 "src/main/c/cext/<lib:truffleruby>",
                 "src/main/c/cext-trampoline/<lib:trufflerubytrampoline>",
                 "src/main/c/bigdecimal/<extsuffix:bigdecimal>",
@@ -773,6 +779,9 @@
                 "lib/cext/include/": [
                     "file:lib/cext/include/*",
                 ],
+                "lib/truffle/": [
+                    "dependency:org.truffleruby.spawnhelper",
+                ],
             },
             "maven": False,
         },
@@ -855,7 +864,7 @@
                     "dependency:org.truffleruby.cext/src/main/c/rbconfig-sizeof/<extsuffix:sizeof>",
                 ],
                 "lib/truffle/": [
-                    "dependency:org.truffleruby.cext/src/main/c/spawn-helper/spawn-helper",
+                    "dependency:org.truffleruby.spawnhelper",
                 ],
             },
             "license": [

src/main/c/Makefile

@@ -17,15 +17,14 @@ endif
 ROOT := $(realpath ../../..)
 RUBY := $(TRUFFLERUBY_BOOTSTRAP_LAUNCHER)
 
-SPAWN_HELPER := spawn-helper/spawn-helper
 TRAMPOLINE := cext-trampoline/libtrufflerubytrampoline.$(SOEXT)
 
 RUBY_HEADERS := $(shell find $(ROOT)/lib/cext/include -name '*.h')
 CEXT_C_FILES := $(shell find cext -name '*.c')
 RBCONFIG := $(ROOT)/lib/truffle/rbconfig.rb
 MKMF := $(ROOT)/lib/mri/mkmf.rb
 LIBTRUFFLERUBY = cext/libtruffleruby.$(SOEXT)
-BASIC_DEPS := Makefile $(SPAWN_HELPER) $(RUBY_HEADERS)
+BASIC_DEPS := Makefile $(RUBY_HEADERS)
 BASIC_EXTCONF_DEPS := $(BASIC_DEPS) $(RBCONFIG) $(MKMF)
 # C extensions link against libtruffleruby (and might do have_func() checks against it), so it needs to be there before.
 # However, if libtruffleruby is recompiled, there is no need to rebuild C extensions, so it's a order-only-prerequisite.
@@ -62,10 +61,6 @@ clean_cexts:
 	$(Q) rm -f debug/Makefile debug/*.o debug/debug.$(DLEXT)
 	$(Q) rm -f rbs/Makefile rbs/*.o rbs/rbs_extension.$(DLEXT)
 
-# spawn-helper
-$(SPAWN_HELPER): spawn-helper/Makefile spawn-helper/spawn-helper.c
-	$(Q) cd spawn-helper && $(MAKE)
-
 # cext-trampoline
 cext-trampoline/trampoline.c: $(CEXT_C_FILES) $(BASIC_DEPS) $(ROOT)/tool/generate-cext-trampoline.rb
 	$(Q) cd $(ROOT) && $(RUBY) tool/generate-cext-trampoline.rb