mercury: Fix CMake 3.15 configure error (#12504)

var/spack/repos/builtin/packages/mercury/fix-cmake-3.15-check_symbol_exists.patch

@@ -0,0 +1,30 @@
+diff --git a/src/util/CMakeLists.txt b/src/util/CMakeLists.txt
+index 69d1dfab..88746473 100644
+--- a/src/util/CMakeLists.txt
++++ b/src/util/CMakeLists.txt
+@@ -16,6 +16,7 @@ set(MERCURY_UTIL_BUILD_INCLUDE_DEPENDENCIES
+ # External dependencies
+ #------------------------------------------------------------------------------
+ include(CheckIncludeFiles)
++include(CheckSymbolExists)
+ include(CheckTypeSize)
+ 
+ # Threads
+@@ -35,7 +36,7 @@ if(CMAKE_USE_PTHREADS_INIT)
+   check_type_size(PTHREAD_MUTEX_ADAPTIVE_NP HG_UTIL_HAS_PTHREAD_MUTEX_ADAPTIVE_NP)
+ 
+   # Detect pthread_condattr_setclock
+-  CHECK_SYMBOL_EXISTS(pthread_condattr_setclock pthread.h HG_UTIL_HAS_PTHREAD_CONDATTR_SETCLOCK)
++  check_symbol_exists(pthread_condattr_setclock pthread.h HG_UTIL_HAS_PTHREAD_CONDATTR_SETCLOCK)
+ endif()
+ 
+ # Rt
+@@ -57,7 +58,7 @@ mark_as_advanced(MERCURY_USE_MONOTONIC_CLOCK)
+ check_include_files("time.h" HG_UTIL_HAS_TIME_H)
+ if(HG_UTIL_HAS_TIME_H)
+   # Detect clock_gettime
+-  CHECK_SYMBOL_EXISTS(clock_gettime time.h HG_UTIL_HAS_CLOCK_GETTIME)
++  check_symbol_exists(clock_gettime time.h HG_UTIL_HAS_CLOCK_GETTIME)
+ endif()
+ 
+ # Detect <sys/time.h>

var/spack/repos/builtin/packages/mercury/package.py

@@ -52,6 +52,10 @@ class Mercury(CMakePackage):
     conflicts('+ofi', when='@:0.9')    # libfabric support was added in 1.0.0
     conflicts('~ofi', when='+udreg')   # udreg option is specific to OFI
 
+    # Fix CMake check_symbol_exists
+    # See https://github.com/mercury-hpc/mercury/issues/299
+    patch('fix-cmake-3.15-check_symbol_exists.patch', when='@:1.0.1')
+
     def cmake_args(self):
         """Populate cmake arguments for Mercury."""
         spec = self.spec