Move sections around to allow porting to windows

We will need to use the environment's CC variable to make decisions
that apply to windows compiling and linking. Therefore we move some
existing sections below the set up of env["CC"] and env["CXX"]

SConstruct

@@ -4,7 +4,6 @@ import os.path
 import platform
 import sys
 
-
 vars = Variables(None, ARGUMENTS)
 vars.Add(PathVariable('DESTDIR', "Root directory to install in (useful for packaging scripts)", None, PathVariable.PathIsDirCreate))
 vars.Add(PathVariable('prefix', "Where to install in the FHS", "/usr/local", PathVariable.PathAccept))
@@ -49,15 +48,6 @@ env['backendsincpath'] = calcInstallPath("$prefix", "include", "hammer", "backen
 env['pkgconfigpath'] = calcInstallPath("$prefix", "lib", "pkgconfig")
 env.ScanReplace('libhammer.pc.in')
 
-env.MergeFlags("-std=gnu99 -Wall -Wextra -Werror -Wno-unused-parameter -Wno-attributes -Wno-unused-variable")
-
-if env['PLATFORM'] == 'darwin':
-    env.Append(SHLINKFLAGS = '-install_name ' + env["libpath"] + '/${TARGET.file}')
-elif os.uname()[0] == "OpenBSD":
-    pass
-else:
-    env.MergeFlags("-lrt")
-
 AddOption("--variant",
           dest="variant",
           nargs=1, type="choice",
@@ -78,20 +68,23 @@ AddOption("--in-place",
           action="store_true",
           help="Build in-place, rather than in the build/<variant> tree")
 
+env["CC"] = os.getenv("CC") or env["CC"]
+env["CXX"] = os.getenv("CXX") or env["CXX"]
 
-dbg = env.Clone(VARIANT='debug')
-dbg.Append(CCFLAGS=['-g'])
+if os.getenv("CC") == "clang" or env['PLATFORM'] == 'darwin':
+    env.Replace(CC="clang",
+                CXX="clang++")
 
-opt = env.Clone(VARIANT='opt')
-opt.Append(CCFLAGS=["-O3"])
+# Language standard and warnings
+env.MergeFlags("-std=gnu99 -Wall -Wextra -Werror -Wno-unused-parameter -Wno-attributes -Wno-unused-variable")
 
-if GetOption("variant") == 'debug':
-    env = dbg
+# Linker options
+if env['PLATFORM'] == 'darwin':
+    env.Append(SHLINKFLAGS = '-install_name ' + env["libpath"] + '/${TARGET.file}')
+elif platform.system() == "OpenBSD":
+    pass
 else:
-    env = opt
-
-env["CC"] = os.getenv("CC") or env["CC"]
-env["CXX"] = os.getenv("CXX") or env["CXX"]
+    env.MergeFlags("-lrt")
 
 if GetOption("coverage"):
     env.Append(CFLAGS=["--coverage"],
@@ -102,9 +95,16 @@ if GetOption("coverage"):
     else:
         env.ParseConfig('llvm-config --ldflags')
 
-if os.getenv("CC") == "clang" or env['PLATFORM'] == 'darwin':
-    env.Replace(CC="clang",
-                CXX="clang++")
+dbg = env.Clone(VARIANT='debug')
+dbg.Append(CCFLAGS=['-g'])
+
+opt = env.Clone(VARIANT='opt')
+opt.Append(CCFLAGS=["-O3"])
+
+if GetOption("variant") == 'debug':
+    env = dbg
+else:
+    env = opt
 
 env["ENV"].update(x for x in os.environ.items() if x[0].startswith("CCC_"))