Revert "Enable PIC rather than relying on environment to do so"

This reverts commit b5b0980.

Author: rhpvorderman

setup.py

@@ -101,21 +101,25 @@ def build_isa_l():
     build_dir = tempfile.mktemp()
     shutil.copytree(ISA_L_SOURCE, build_dir)
 
+    # Build environment is a copy of OS environment to allow user to influence
+    # it.
+    build_env = os.environ.copy()
+    if SYSTEM_IS_UNIX:
+        build_env["CFLAGS"] = build_env.get("CFLAGS", "") + " -fPIC"
     if hasattr(os, "sched_getaffinity"):
         cpu_count = len(os.sched_getaffinity(0))
     else:  # sched_getaffinity not available on all platforms
         cpu_count = os.cpu_count() or 1  # os.cpu_count() can return None
+    run_args = dict(cwd=build_dir, env=build_env)
     if SYSTEM_IS_UNIX:
         make_cmd = "make"
         if SYSTEM_IS_BSD:
             make_cmd = "gmake"
-        subprocess.run(os.path.join(build_dir, "autogen.sh"), cwd=build_dir)
-        subprocess.run(
-            [os.path.join(build_dir, "configure"), "--enable-pic"],
-            cwd=build_dir)
-        subprocess.run([make_cmd, "-j", str(cpu_count)], cwd=build_dir)
+        subprocess.run(os.path.join(build_dir, "autogen.sh"), **run_args)
+        subprocess.run([os.path.join(build_dir, "configure")], **run_args)
+        subprocess.run([make_cmd, "-j", str(cpu_count)], **run_args)
     elif SYSTEM_IS_WINDOWS:
-        subprocess.run(["nmake", "/f", "Makefile.nmake"], cwd=build_dir)
+        subprocess.run(["nmake", "/f", "Makefile.nmake"], **run_args)
     else:
         raise NotImplementedError(f"Unsupported platform: {sys.platform}")
     shutil.copytree(os.path.join(build_dir, "include"),