Bug 1513798 - Don't set HOST_{CC,CXX,CPP} and CPP. r=nalexander

CPP/HOST_CPP were probably not necessary already, but now that we leave
it to configure to figure out the appropriate compiler flags, we don't
need to set HOST_CC/HOST_CXX to remove the flags from CC/CXX.

Differential Revision: https://phabricator.services.mozilla.com/D14382

build/macosx/cross-mozconfig.common

@@ -23,7 +23,6 @@ CROSS_PRIVATE_FRAMEWORKS=$CROSS_SYSROOT/System/Library/PrivateFrameworks
 
 export CC="$topsrcdir/clang/bin/clang"
 export CXX="$topsrcdir/clang/bin/clang++"
-export CPP="$topsrcdir/clang/bin/clang -E"
 export LLVMCONFIG=$topsrcdir/clang/bin/llvm-config
 export LDFLAGS="-Wl,-syslibroot,$CROSS_SYSROOT"
 export BINDGEN_CFLAGS="-isysroot $CROSS_SYSROOT"
@@ -33,9 +32,6 @@ export MKFSHFS=$topsrcdir/hfsplus-tools/newfs_hfs
 export DMG_TOOL=$topsrcdir/dmg/dmg
 export HFS_TOOL=$topsrcdir/dmg/hfsplus
 
-export HOST_CC="$topsrcdir/clang/bin/clang"
-export HOST_CXX="$topsrcdir/clang/bin/clang++"
-export HOST_CPP="$topsrcdir/clang/bin/clang -E"
 export HOST_CFLAGS="-g"
 export HOST_CXXFLAGS="-g"
 export HOST_LDFLAGS="-g"