Should / must we do anything about the issue? At least Python builds
with a C89 compiler except of ssl and socket module. Those modules
include non C89 compliant header files from the OS (bluetooth and tpic).

$ LC_ALL="C" CC="gcc -std=c89" make
gcc -std=c89 -pthread -c -fno-strict-aliasing -DNDEBUG -g  -O3 -Wall
-Wstrict-prototypes  -I. -IInclude -I./Include   -DPy_BUILD_CORE -o
Objects/object.o Objects/object.c                                      
                             
Objects/object.c: In function 'internal_print':                        
                                               
Objects/object.c:295: warning: ignoring return value of 'fwrite',
declared with attribute warn_unused_result           
Objects/object.c:304: warning: ignoring return value of 'fwrite',
declared with attribute warn_unused_result           
gcc -std=c89 -pthread -c -fno-strict-aliasing -DNDEBUG -g  -O3 -Wall
-Wstrict-prototypes  -I. -IInclude -I./Include   -DPy_BUILD_CORE -o
Python/marshal.o Python/marshal.c                                      
                             
Python/marshal.c: In function 'w_string':                              
                                               
Python/marshal.c:90: warning: ignoring return value of 'fwrite',
declared with attribute warn_unused_result            
gcc -std=c89 -pthread -c -fno-strict-aliasing -DNDEBUG -g  -O3 -Wall
-Wstrict-prototypes  -I. -IInclude -I./Include   -DPy_BUILD_CORE -o
Modules/main.o Modules/main.c                                          
                             
Modules/main.c: In function 'usage':                                   
                                               
Modules/main.c:134: warning: format not a string literal and no format
arguments                                       
Modules/main.c:135: warning: format not a string literal and no format
arguments                                       
Modules/main.c:136: warning: format not a string literal and no format
arguments