cmake: compiler: add double promotion warning

Too many times, code is pushed that includes floats that really
becomes doubles and C implicit promotion rules will want to make
floats into doubles very easily. As zephyr primarily targets
low-end process that may not have a double precision floating
point unit, enable this flag globally for now.

Signed-off-by: Ryan McClelland <ryanmcclelland@meta.com>

cmake/compiler/arcmwdt/compiler_flags.cmake

@@ -33,6 +33,9 @@ set_compiler_property(PROPERTY warning_base
                       -Wno-typedef-redefinition
 )
 
+# C implicit promotion rules will want to make floats into doubles very easily
+check_set_compiler_property(APPEND PROPERTY warning_base -Wdouble-promotion)
+
 check_set_compiler_property(APPEND PROPERTY warning_base -Wno-pointer-sign)
 
 # Prohibit void pointer arithmetic. Illegal in C99

cmake/compiler/clang/compiler_flags.cmake

@@ -45,6 +45,9 @@ check_set_compiler_property(PROPERTY warning_base
                             -Wno-deprecated-non-prototype
 )
 
+# C implicit promotion rules will want to make floats into doubles very easily
+check_set_compiler_property(APPEND PROPERTY warning_base -Wdouble-promotion)
+
 check_set_compiler_property(APPEND PROPERTY warning_base -Wno-pointer-sign)
 
 # Prohibit void pointer arithmetic. Illegal in C99

cmake/compiler/gcc/compiler_flags.cmake

@@ -32,6 +32,9 @@ check_set_compiler_property(PROPERTY warning_base
     "SHELL:-Wformat -Wno-format-zero-length"
 )
 
+# C implicit promotion rules will want to make floats into doubles very easily
+check_set_compiler_property(APPEND PROPERTY warning_base -Wdouble-promotion)
+
 check_set_compiler_property(APPEND PROPERTY warning_base -Wno-pointer-sign)
 
 # Prohibit void pointer arithmetic. Illegal in C99