[CMake] Add R__HAS_CLAD preprocessor macro

To avoid warnings about unknown pragmas, it's useful to have a
`R__HAS_CLAD` macro defined in the interpreter, so that Clad pragmas can
be conditional on Clad being available.

Author: guitargeek

cmake/modules/RootConfiguration.cmake

@@ -355,6 +355,11 @@ if(lz4)
 else()
   set(haslz4compression undef)
 endif()
+if(clad)
+  set(hasclad define)
+else()
+  set(hasclad undef)
+endif()
 if(cocoa)
   set(hascocoa define)
 else()

config/RConfigure.in

@@ -35,6 +35,7 @@
 #@hasmathmore@ R__HAS_MATHMORE   /**/
 #@haspthread@ R__HAS_PTHREAD    /**/
 #@hasxft@ R__HAS_XFT    /**/
+#@hasclad@ R__HAS_CLAD    /**/
 #@hascocoa@ R__HAS_COCOA    /**/
 #@hasvc@ R__HAS_VC    /**/
 #@hasvdt@ R__HAS_VDT    /**/

roofit/roofitcore/inc/RooFit/Detail/MathFuncs.h

@@ -177,7 +177,7 @@ template <typename DoubleArray>
 double constraintSum(DoubleArray comp, unsigned int compSize)
 {
    double sum = 0;
-   #ifdef __CLING__
+   #if defined(__CLING__) && defined(R__HAS_CLAD)
    #pragma clad checkpoint loop
    #endif
    for (unsigned int i = 0; i < compSize; i++) {
@@ -367,7 +367,7 @@ double flexibleInterp(unsigned int code, ParamsArray params, unsigned int n, Dou
                       double boundary, double nominal, int doCutoff)
 {
    double total = nominal;
-   #ifdef __CLING__
+   #if defined(__CLING__) && defined(R__HAS_CLAD)
    #pragma clad checkpoint loop
    #endif
    for (std::size_t i = 0; i < n; ++i) {