Add NOMINMAX definitions when compiling with MSVC (#283)

This adds NOMINMAX as a public/interface definition to the targets `opencensus_common_stats_object` and `opencensus_stats_core`
to unbreak the build with MSVC.

Author: meastp

opencensus/common/internal/CMakeLists.txt

@@ -24,6 +24,10 @@ opencensus_lib(common_random
 
 opencensus_lib(common_stats_object DEPS absl::time)
 
+# Define NOMINMAX to fix build errors when compiling with MSVC.
+target_compile_definitions(opencensus_common_stats_object INTERFACE
+                           $<$<CXX_COMPILER_ID:MSVC>:NOMINMAX>)
+
 opencensus_lib(common_string_vector_hash)
 
 opencensus_test(common_random_test random_test.cc common_random)

opencensus/stats/CMakeLists.txt

@@ -54,6 +54,10 @@ opencensus_lib(stats_core
                absl::optional
                absl::span)
 
+# Define NOMINMAX to fix build errors when compiling with MSVC.
+target_compile_definitions(opencensus_stats_core PUBLIC
+                           $<$<CXX_COMPILER_ID:MSVC>:NOMINMAX>)
+
 opencensus_lib(stats_recording
                SRCS
                internal/recording.cc