Fixes to building packaged libsqlite3.

Ensure that we are linking to the packaged library, even in cases where
libsqlite is available in the system.

 * Move or replace all mkmf calls that would add -lsqlite3 to the command line:
   pkg_config, find_library
 * Explicitly link against the built sqlite3 as a static library.

Author: Ben Li

ext/sqlite3/extconf.rb

@@ -45,6 +45,8 @@ def sqlcipher?
       def configure_system_libraries
         pkg_config(libname)
         append_cppflags("-DUSING_SQLCIPHER") if sqlcipher?
+
+        abort_could_not_find(libname) unless find_library(libname, "sqlite3_libversion_number", "sqlite3.h")
       end
 
       def configure_packaged_libraries
@@ -83,19 +85,20 @@ def configure_packaged_libraries
 
           lib_path = File.join(recipe.path, "lib")
           pcfile = File.join(lib_path, "pkgconfig", "sqlite3.pc")
-          abort_pkg_config("pkg_config") unless pkg_config(pcfile)
+          libfile = File.join(lib_path, "libsqlite3.a")
 
-          # see https://bugs.ruby-lang.org/issues/18490
-          ldflags = xpopen(["pkg-config", "--libs", "--static", pcfile], err: [:child, :out], &:read)
-          abort_pkg_config("xpopen") unless $?.success?
-          ldflags = ldflags.split
+          # Avoid one-arg pkg_config call adding -lsqlite3
+          pkg_cflags = pkg_config(pcfile, "cflags")
+          # Include directories are prioritized over system defaults
+          append_cflags(pkg_cflags)
 
-          # see https://github.com/flavorjones/mini_portile/issues/118
-          "-L#{lib_path}".tap do |lib_path_flag|
-            ldflags.prepend(lib_path_flag) unless ldflags.include?(lib_path_flag)
-          end
+          # Force static linkage to packaged libsqlite3
+          append_ldflags(libfile)
 
-          ldflags.each { |ldflag| append_ldflags(ldflag) }
+          # Pull dependencies but not the library itself
+          pkg_libs = pkg_config(pcfile, "libs-only-l", "static")
+          pkg_libs.sub!(/\w*-lsqlite3\w*/, "")
+          append_ldflags(pkg_libs)
 
           append_cppflags("-DUSING_PACKAGED_LIBRARIES")
           append_cppflags("-DUSING_PRECOMPILED_LIBRARIES") if cross_build?
@@ -113,8 +116,6 @@ def configure_extension
           abort_could_not_find("sqlite3.h")
         end
 
-        abort_could_not_find(libname) unless find_library(libname, "sqlite3_libversion_number", "sqlite3.h")
-
         # Truffle Ruby doesn't support this yet:
         # https://github.com/oracle/truffleruby/issues/3408
         have_func("rb_enc_interned_str_cstr")