diff -ur Python-3.7.3/setup.py Python-3.7.3+iPhone/setup.py
--- Python-3.7.3/setup.py	2019-03-25 10:21:05.000000000 -1000
+++ Python-3.7.3+iPhone/setup.py	2019-05-07 14:47:15.000000000 -1000
@@ -98,7 +98,7 @@
     cflags = sysconfig.get_config_var('CFLAGS')
     m = re.search(r'-isysroot\s+(\S+)', cflags)
     if m is None:
-        sysroot = '/'
+        sysroot = os.environ['PKG_ROOT'] or '/'
     else:
         sysroot = m.group(1)
     return sysroot
@@ -611,11 +611,10 @@
             # Add the sysroot paths. 'sysroot' is a compiler option used to
             # set the logical path of the standard system headers and
             # libraries.
-            lib_dirs = (self.compiler.library_dirs +
-                        sysroot_paths(('LDFLAGS', 'CC'), system_lib_dirs))
-            inc_dirs = (self.compiler.include_dirs +
-                        sysroot_paths(('CPPFLAGS', 'CFLAGS', 'CC'),
-                                      system_include_dirs))
+            lib_dirs = ([os.getenv('PKG_ROOT') + '/usr/lib'] +
+                        os.getenv('LIBRARY_PATH').split(':'))
+            inc_dirs = ([os.getenv('PKG_ROOT') + '/usr/include'] +
+                        os.getenv('CPATH').split(':'))
         exts = []
         missing = []