Get the environment propagated to scons forked childs, and correct the dicom plugin about
a typedef of size_t that failed at least on x86_64-linux.

diff --git a/SConstruct b/SConstruct
index 16eccd9..603e931 100644
--- a/SConstruct
+++ b/SConstruct
@@ -7,8 +7,7 @@ else:
     cppflags = ['-O2']
     variant = 'Release'
 
-env = Environment(LIBPATH=[],
-                  CPPFLAGS = cppflags)
+env = Environment(ENV = os.environ)
 
 env['SBOX'] = False
 
diff --git a/giv/SConstruct b/giv/SConstruct
index 047839a..2c267aa 100644
--- a/giv/SConstruct
+++ b/giv/SConstruct
@@ -3,8 +3,9 @@
 
 import sys
 import re
+import os
 
-env = Environment()
+env = Environment(ENV = os.environ)
 
 src = ["giv.c",
        "giv-backstore.c",
diff --git a/src/plugins/dcmtk/SConstruct.standalone b/src/plugins/dcmtk/SConstruct.standalone
index ffce001..74246f8 100644
--- a/src/plugins/dcmtk/SConstruct.standalone
+++ b/src/plugins/dcmtk/SConstruct.standalone
@@ -1,4 +1,6 @@
-env = Environment()
+import os
+
+env = Environment(ENV = os.environ)
 
 variant = "Debug"