meson: migrate -Werror into meson's werror option

[lumag]

Follow Meson recomendations and use --werror option instead of hardcoding -Werror.

[superna9999]

@lumag you should add it to the default_options array instead:

diff --git a/meson.build b/meson.build
index 0392b0e..04228f0 100644
--- a/meson.build
+++ b/meson.build
@@ -7,6 +7,7 @@ project('cdba',
        default_options: [
             'warning_level=2', # sets -Wextra
             'buildtype=release',
+            'werror=true',
         ])
 
 # Set advanced compiler flags
@@ -26,8 +27,7 @@ compiler_cflags = ['-Wno-unused-parameter',
 
 # TODO add clang specific options
 if compiler.get_id() == 'gcc'
-       compiler_cflags += ['-Werror',  # Only set it on GCC
-                           '-Wformat-signedness',
+       compiler_cflags += ['-Wformat-signedness',
                            '-Wduplicated-cond',
                            '-Wduplicated-branches',
                            '-Wvla-larger-than=1',

[lumag]

@lumag you should add it to the default_options array instead:

No, I don't want to have that in defaults. Let's keep it for CI only (as @calebccff did in #37 )

[superna9999]

Close in favor of #37