build: remove symbol visibility from capture static library

The visibility of symbols was getting extracted from the .a into the
libraries that link_whole the archive. We can simply disable the visibility
from the .a with a custom config.h.meson which avoids it for the capture
library. Since we already double-compile those sources for the shared
library, the shared library visibility is not affected.

This was tested by compiling a simple library which calls
sysprof_clock_init() and ensuring that no extra symbols were found with
`nm libfoo.so | grep ' T '`.

Fixes #60

config.h.meson

@@ -0,0 +1,55 @@
+#mesondefine API_VERSION_S
+
+#mesondefine DEBUGDIR
+
+#mesondefine DEVELOPMENT_BUILD
+
+#mesondefine ENABLE_LIBUNWIND
+
+#mesondefine ENABLE_NLS
+
+#mesondefine GETTEXT_PACKAGE
+
+#mesondefine HAVE_EXECINFO_H
+
+#mesondefine HAVE_PERF_CLOCKID
+
+#mesondefine HAVE_POLKIT
+
+#mesondefine HAVE_POLKIT_AGENT
+
+#mesondefine HAVE_REALLOCARRAY
+
+#mesondefine HAVE_STDATOMIC_H
+
+#mesondefine HAVE_STRLCPY
+
+#mesondefine HAVE_UNW_SET_CACHE_SIZE
+
+#mesondefine LOCALEDIR
+
+#mesondefine PACKAGE
+
+#mesondefine PACKAGE_BUGREPORT
+
+#mesondefine PACKAGE_LIBDIR
+
+#mesondefine PACKAGE_LIBEXECDIR
+
+#mesondefine PACKAGE_LOCALE_DIR
+
+#mesondefine PACKAGE_NAME
+
+#mesondefine PACKAGE_STRING
+
+#mesondefine PACKAGE_TARNAME
+
+#mesondefine PACKAGE_VERSION
+
+#mesondefine SYMBOLIC_VERSION
+
+#mesondefine VERSION
+
+#ifndef SYSPROF_CAPTURE_COMPILATION
+#mesondefine _SYSPROF_EXTERN
+#endif

meson.build

@@ -201,6 +201,7 @@ subdir('help')
 subdir('po')
 
 configure_file(
+          input: 'config.h.meson',
          output: 'config.h',
   configuration: config_h
 )