SERVER-27675 Make all targets depend on the allocator shim to topsort it last

src/third_party/SConscript

@@ -1,5 +1,7 @@
 # -*- mode: python -*-
 
+import SCons
+
 import libdeps
 import json
 
@@ -208,6 +210,42 @@ def injectThirdParty(thisEnv, libraries=[], parts=[]):
 
 env.AddMethod(injectThirdParty, 'InjectThirdParty')
 
+# In a dynamic build, force everything to depend on shim_allocator, so
+# that it topsorts to the end of the list.  We are totally relying on
+# the fact that we are altering the env from src/SConscript
+if get_option('link-model').startswith("dynamic"):
+
+    for builder_name in ('Program', 'SharedLibrary', 'LoadableModule', 'StaticLibrary'):
+        builder = env['BUILDERS'][builder_name]
+        base_emitter = builder.emitter
+
+        def add_shim_allocator_hack(target, source, env):
+
+            # If we allowed conftests to become dependent, any TryLink
+            # that happened after we made the below modifications would
+            # cause the configure steps to try to compile tcmalloc and any
+            # of its dependencies. Oops!
+            if any('conftest' in str(t) for t in target):
+                return target, source
+
+            # It is possible that 'env' isn't a unique
+            # OverrideEnvironment, since if you didn't pass any kw args
+            # into your builder call, you just reuse the env you were
+            # called with. That could mean that we see the same
+            # envirnoment here multiple times. But that is really OK,
+            # since the operation we are performing would be performed on
+            # all of them anyway. The flag serves as a way to disable the
+            # auto-injection for the handful of libraries where we must do
+            # so to avoid forming a cycle.
+            if not env.get('DISABLE_ALLOCATOR_SHIM_INJECTION', False):
+                lds = env.get('LIBDEPS', [])
+                lds.append('$BUILD_DIR/third_party/shim_allocator')
+                env['LIBDEPS'] = lds
+
+            return target, source
+
+        builder.emitter = SCons.Builder.ListEmitter([add_shim_allocator_hack, base_emitter])
+
 env = env.Clone()
 
 murmurEnv = env.Clone()
@@ -249,7 +287,12 @@ if use_libunwind:
         target="shim_unwind",
         source=[
             'shim_unwind.cpp',
-        ])
+        ],
+        # We don't want the shim_allocator hack to apply to this library, since
+        # otherwise we would create a loop, since tcmalloc might use us. That should
+        # be OK, unless libunwind had static initializers that invoked malloc.
+        DISABLE_ALLOCATOR_SHIM_INJECTION=True,
+    )
 
 if use_system_version_of_library("fmt"):
     fmtEnv = env.Clone(
@@ -493,7 +536,9 @@ gperftoolsEnv.Library(
     target="shim_allocator",
     source=[
         "shim_allocator.cpp",
-    ])
+    ],
+    DISABLE_ALLOCATOR_SHIM_INJECTION=True,
+)
 
 
 if use_system_version_of_library("stemmer"):