Consolidate preload logic. Implement logic into preload.sh to cater to

Darwin issues with empty incoming DYLD_INSERT_LIBRARIES variable.

build/common.mk

@@ -1148,14 +1148,10 @@ ifeq ($(ESMF_OS),MinGW)
 ESMF_LIB_SUFFIX       = lib
 endif
 
-# - Shared library and preload environment variable
+# - Shared library
 ESMF_SL_SUFFIX        = so
-ESMF_PRELOAD          = LD_PRELOAD
-ESMF_PRELOAD_DELIMIT  = ' '
 ifeq ($(ESMF_OS),Darwin)
 ESMF_SL_SUFFIX        = dylib
-ESMF_PRELOAD          = DYLD_INSERT_LIBRARIES
-ESMF_PRELOAD_DELIMIT  = ':'
 endif
 ifeq ($(ESMF_OS),Cygwin)
 ESMF_SL_SUFFIX        = dll.a
@@ -2027,9 +2023,11 @@ ESMF_TRACE_LDPRELOAD := $(ESMF_LIBDIR)/libesmftrace_preload.$(ESMF_SL_SUFFIX)
 ESMF_PRELOADSCRIPT = $(ESMF_LIBDIR)/preload.sh
 
 ifneq ($(ESMF_OS),Darwin)
-ESMF_ENV_PRELOAD = LD_PRELOAD
+ESMF_ENV_PRELOAD          = LD_PRELOAD
+ESMF_ENV_PRELOAD_DELIMIT  = ' '
 else
-ESMF_ENV_PRELOAD = DYLD_INSERT_LIBRARIES
+ESMF_ENV_PRELOAD          = DYLD_INSERT_LIBRARIES
+ESMF_ENV_PRELOAD_DELIMIT  = ':'
 endif
 
 # MPI implementations do not pick up LD_PRELOAD
@@ -2052,7 +2050,11 @@ endif
 build_preload_script:
 	-@echo "#!/bin/sh" > $(ESMF_PRELOADDIR)/preload.sh
 	-@echo "# Script to preload ESMF dynamic trace library" >> $(ESMF_PRELOADDIR)/preload.sh
-	-@echo 'env $(ESMF_PRELOAD)="$$$(ESMF_PRELOAD)$(ESMF_PRELOAD_DELIMIT)$(ESMF_PRELOADDIR)/libesmftrace_preload.$(ESMF_SL_SUFFIX)" $$*' >> $(ESMF_PRELOADDIR)/preload.sh
+	-@echo 'if [ "$(ESMF_ENV_PRELOAD)" != "" ]; then' >> $(ESMF_PRELOADDIR)/preload.sh
+	-@echo 'env $(ESMF_ENV_PRELOAD)="$$$(ESMF_ENV_PRELOAD)$(ESMF_ENV_PRELOAD_DELIMIT)$(ESMF_PRELOADDIR)/libesmftrace_preload.$(ESMF_SL_SUFFIX)" $$*' >> $(ESMF_PRELOADDIR)/preload.sh
+	-@echo 'else' >> $(ESMF_PRELOADDIR)/preload.sh
+	-@echo 'env $(ESMF_ENV_PRELOAD)="$(ESMF_PRELOADDIR)/libesmftrace_preload.$(ESMF_SL_SUFFIX)" $$*' >> $(ESMF_PRELOADDIR)/preload.sh
+	-@echo 'fi' >> $(ESMF_PRELOADDIR)/preload.sh
 	chmod 755 $(ESMF_PRELOADDIR)/preload.sh
 
 ESMF_TRACE_STATICLINKLIBS := -lesmftrace_static