add -shared to the PCH flags to prevent error when using the MESA SDK

meson.build

 ###########################################################
 # meson build file for binary_c
 #
-# (c) Robert Izzard 12/11/2020
+# (c) Robert Izzard 04/08/2021
 #
 # Known to work with binary_c 2.2.pre1 using gcc and clang.
 #
@@ -198,7 +198,6 @@ foreach buggy_perl_version : buggy_perls
     endif
 endforeach
 
-
 ############################################################
 # compiler object
 #
@@ -1375,11 +1374,12 @@ if get_option('usepch') == true
               _opt,
               _pic,
               _incdirs,
+              '-shared', # required to prevent MESA SDK errors
               '-MT', 'binary_c.h.gch',
               '-MMD',
               '-MP',
               '-MF', _depfile_path,
-              '-x', 'c-header'
+              '-x', 'c-header',
             ]
         pch_sourcefiles = [ _gch ]
         cflags += [

src/binary_c.h

@@ -92,12 +92,3 @@
 
 
 #endif //BINARY_C_H
-
-/*
-#define __dummy_function_concat(A,B) A##B
-#define __dummy_function2(A) \
-    static void MAYBE_UNUSED __dummy_function_concat(__dummy_name,A)(void); \
-    static void MAYBE_UNUSED __dummy_function_concat(__dummy_name,A)(void){return;}
-#define __dummy_function __dummy_function2(__COUNTER__)
-__dummy_function
-*/