Honor environement (#2949)

* Honor environement

Pass environment through SCons. For instance, this is required to pass CCACHE_* variabled to ccache.

* If carrying over all environment variables, no need to handle any individually.

Author: AMDmi3

SConstruct

@@ -1,17 +1,11 @@
 import os
 
-# Load any environment variables that alter the build.
-env = Environment()
-if 'CCFLAGS' in os.environ:
-	env.Append(CCFLAGS = os.environ['CCFLAGS'])
+# Load environment variables, including some that should be renamed.
+env = Environment(ENV = os.environ)
 if 'CXXFLAGS' in os.environ:
 	env.Append(CCFLAGS = os.environ['CXXFLAGS'])
-if 'CPPFLAGS' in os.environ:
-	env.Append(CPPFLAGS = os.environ['CPPFLAGS'])
 if 'LDFLAGS' in os.environ:
 	env.Append(LINKFLAGS = os.environ['LDFLAGS'])
-if 'CPPPATH' in os.environ:
-	env.Append(CPPPATH = os.environ['CPPPATH'])
 
 # The Steam runtime has an out-of-date libstdc++, so link it in statically:
 if 'SCHROOT_CHROOT_NAME' in os.environ and 'steamrt' in os.environ['SCHROOT_CHROOT_NAME']:
@@ -56,11 +50,6 @@ else:
 	env.Append(LIBS = "mad")
 
 
-# Work with clang's static analyzer:
-env["CC"] = os.getenv("CC") or env["CC"]
-env["CXX"] = os.getenv("CXX") or env["CXX"]
-env["ENV"].update(x for x in os.environ.items() if x[0].startswith("CCC_"))
-
 buildDirectory = env["BUILDDIR"] + "/" + env["mode"]
 VariantDir(buildDirectory, "source", duplicate = 0)