Fix build on Docker containers

Fixes #3244

.venv/lib64

@@ -0,0 +1 @@
+lib

.venv/pip-selfcheck.json

@@ -0,0 +1 @@
+{"last_check":"2018-07-09T07:16:29Z","pypi_version":"10.0.1"}

.venv/pyvenv.cfg

@@ -0,0 +1,3 @@
+home = /usr/local/bin
+include-system-site-packages = false
+version = 3.6.5

setup.py

@@ -12,6 +12,7 @@
 import os
 import platform as plat
 import re
+import string
 import struct
 import subprocess
 import sys
@@ -74,6 +75,27 @@ def _dbg(s, tp=None):
         print(s)
 
 
+def _find_strings_in_binary(filename, min=5):
+    # based on https://stackoverflow.com/a/17197027/199332
+    if sys.version_info[0] == 3:
+        fp = open(filename, errors="ignore")
+    else:
+        fp = open(filename, "rb")
+    try:
+        result = ""
+        for c in fp.read():
+            if c in string.printable:
+                result += c
+                continue
+            if len(result) >= min:
+                yield result
+            result = ""
+        if len(result) >= min:  # catch result at EOF
+            yield result
+    finally:
+        fp.close()
+
+
 def _add_directory(path, subdir, where=None):
     if subdir is None:
         return
@@ -334,60 +356,20 @@ def build_extensions(self):
                 _add_directory(include_dirs, "/usr/X11/include")
 
         elif sys.platform.startswith("linux"):
-            arch_tp = (plat.processor(), plat.architecture()[0])
-            # This should be correct on debian derivatives.
-            if os.path.exists('/etc/debian_version'):
-                # If this doesn't work, don't just silently patch
-                # downstream because it's going to break when people
-                # try to build pillow from source instead of
-                # installing from the system packages.
-                self.add_multiarch_paths()
-
-            elif arch_tp == ("x86_64", "32bit"):
-                # Special Case: 32-bit build on 64-bit machine.
-                _add_directory(library_dirs, "/usr/lib/i386-linux-gnu")
-            else:
-                libdirs = {
-                    'x86_64':  ["/lib64", "/usr/lib64",
-                                "/usr/lib/x86_64-linux-gnu"],
-                    '64bit':   ["/lib64", "/usr/lib64",
-                                "/usr/lib/x86_64-linux-gnu"],
-                    'i386':    ["/usr/lib/i386-linux-gnu"],
-                    'i686':    ["/usr/lib/i386-linux-gnu"],
-                    '32bit':   ["/usr/lib/i386-linux-gnu"],
-                    'aarch64': ["/usr/lib64", "/usr/lib/aarch64-linux-gnu"],
-                    'arm':     ["/usr/lib/arm-linux-gnueabi"],
-                    'armv71':  ["/usr/lib/arm-linux-gnueabi"],
-                    'armv7l':  ["/usr/lib"],
-                    'ppc64':   ["/usr/lib64", "/usr/lib/ppc64-linux-gnu",
-                                "/usr/lib/powerpc64-linux-gnu"],
-                    'ppc64le':   ["/usr/lib64"],
-                    'ppc':     ["/usr/lib/ppc-linux-gnu",
-                                "/usr/lib/powerpc-linux-gnu"],
-                    's390x':   ["/usr/lib64", "/usr/lib/s390x-linux-gnu"],
-                    's390':    ["/usr/lib/s390-linux-gnu"],
-                    }
-
-                for platform_ in arch_tp:
-                    dirs = libdirs.get(platform_, None)
-                    if not dirs:
-                        continue
-                    for path in dirs:
-                        _add_directory(library_dirs, path)
-                    break
-
-                else:
-                    raise ValueError(
-                        "Unable to identify Linux platform: `%s`" % platform_)
-
-                # termux support for android.
-                # system libraries (zlib) are installed in /system/lib
-                # headers are at $PREFIX/include
-                # user libs are at $PREFIX/lib
-                if os.environ.get('ANDROID_ROOT', None):
-                    _add_directory(library_dirs,
-                                   os.path.join(os.environ['ANDROID_ROOT'],
-                                                'lib'))
+            ld_so_cache = '/etc/ld.so.cache'
+            if os.path.isfile(ld_so_cache):
+                for candidate in _find_strings_in_binary(ld_so_cache):
+                    if candidate[0] == '/':
+                        dirname = os.path.dirname(candidate)
+                        _add_directory(library_dirs, dirname)
+            # termux support for android.
+            # system libraries (zlib) are installed in /system/lib
+            # headers are at $PREFIX/include
+            # user libs are at $PREFIX/lib
+            if os.environ.get('ANDROID_ROOT', None):
+                _add_directory(library_dirs,
+                                os.path.join(os.environ['ANDROID_ROOT'],
+                                            'lib'))
 
         elif sys.platform.startswith("gnu"):
             self.add_multiarch_paths()