Fix include common.fypp

Author: jvdp1

include/common.fypp

@@ -151,7 +151,7 @@ $:"s" if cmplx=="c" else "d" if cmplx=="z" else "x" if cmplx=="y" else "q" if cm
 #:set BITSET_INIT = ["" for k in BITSET_KINDS]
 
 #! Bitset CPP directive to be considered during templating
-#:set BITSET_CPPS = ["STDLIB_BITSET" for k in BITSET_KINDS]
+#:set BITSET_CPPS = ["STDLIB_BITSET == 1" for k in BITSET_KINDS]
 
 #! Collected (kind, type) tuples for bitset types
 #:set BITSET_KINDS_TYPES = list(zip(BITSET_KINDS, BITSET_TYPES, BITSET_INIT, BITSET_CPPS))
@@ -496,7 +496,7 @@ ${indent}$do ${varname}$${n+1+dim_offset-i}$ = lbound(${matname}$, ${n+1+dim_off
 #!
 #:def generate_cpp(code, cpp_var)
   #:if cpp_var != ""
-#ifdef ${cpp_var}$
+#if ${cpp_var}$
   #:endif
   $:code
   #:if cpp_var != ""