Remove deadcode in the build script

Reviewed By: ngorogiannis

Differential Revision: D17906654

fbshipit-source-id: 7a2817a48

build-infer.sh

@@ -43,7 +43,6 @@ function usage() {
 BUILD_CLANG=${BUILD_CLANG:-no}
 BUILD_JAVA=${BUILD_JAVA:-no}
 INFER_CONFIGURE_OPTS=${INFER_CONFIGURE_OPTS:-""}
-INFER_OPAM_SWITCH=${INFER_OPAM_SWITCH:-$INFER_OPAM_SWITCH_DEFAULT}
 INTERACTIVE=${INTERACTIVE:-yes}
 JOBS=${JOBS:-$NCPU}
 ONLY_SETUP_OPAM=${ONLY_SETUP_OPAM:-no}