fix(cmake): incorrect detection of Emscripten

Signed-off-by: Henry Schreiner <[email protected]>

tools/pybind11Common.cmake

@@ -79,7 +79,7 @@ set_property(
 # _pybind11_no_exceptions is a private mechanism to disable this addition.
 # Please open an issue if you need to use it; it will be removed if no one
 # needs it.
-if(CMAKE_SYSTEM_PROCESSOR MATCHES emscripten AND NOT _pybind11_no_exceptions)
+if(CMAKE_SYSTEM_NAME MATCHES Emscripten AND NOT _pybind11_no_exceptions)
   if(CMAKE_VERSION VERSION_LESS 3.13)
     message(WARNING "CMake 3.13+ is required to build for Emscripten. Some flags will be missing")
   else()
@@ -348,7 +348,7 @@ function(_pybind11_generate_lto target prefer_thin_lto)
 
     if(CMAKE_SYSTEM_PROCESSOR MATCHES "ppc64le" OR CMAKE_SYSTEM_PROCESSOR MATCHES "mips64")
       # Do nothing
-    elseif(CMAKE_SYSTEM_PROCESSOR MATCHES emscripten)
+    elseif(CMAKE_SYSTEM_NAME MATCHES Emscripten)
       # This compile is very costly when cross-compiling, so set this without checking
       set(PYBIND11_LTO_CXX_FLAGS "-flto${thin}${cxx_append}")
       set(PYBIND11_LTO_LINKER_FLAGS "-flto${thin}${linker_append}")