all around: disable print_system_libs in calls to pkg-config

By default, pkg-config-rs sets the PKG_CONFIG_ALLOW_SYSTEM_LIBS
environment variable
(https://github.com/alexcrichton/pkg-config-rs/pull/35), which leads
to eg /usr/lib being present in the middle of the final command,
in turn leading to issues when working in an uninstalled environment,
where libraries that are also present system-wide do not get linked
against.

gstreamer-app-sys/build.rs

@@ -45,6 +45,7 @@ fn find() -> Result<(), Error> {
 
     let mut config = Config::new();
     config.atleast_version(version);
+    config.print_system_libs(false);
     if hardcode_shared_libs {
         config.cargo_metadata(false);
     }

gstreamer-audio-sys/build.rs

@@ -45,6 +45,7 @@ fn find() -> Result<(), Error> {
 
     let mut config = Config::new();
     config.atleast_version(version);
+    config.print_system_libs(false);
     if hardcode_shared_libs {
         config.cargo_metadata(false);
     }

gstreamer-base-sys/build.rs

@@ -49,6 +49,7 @@ fn find() -> Result<(), Error> {
 
     let mut config = Config::new();
     config.atleast_version(version);
+    config.print_system_libs(false);
     if hardcode_shared_libs {
         config.cargo_metadata(false);
     }

gstreamer-mpegts-sys/build.rs

@@ -33,6 +33,7 @@ fn find() -> Result<(), Error> {
 
     let mut config = Config::new();
     config.atleast_version(version);
+    config.print_system_libs(false);
     if hardcode_shared_libs {
         config.cargo_metadata(false);
     }

gstreamer-net-sys/build.rs

@@ -45,6 +45,7 @@ fn find() -> Result<(), Error> {
 
     let mut config = Config::new();
     config.atleast_version(version);
+    config.print_system_libs(false);
     if hardcode_shared_libs {
         config.cargo_metadata(false);
     }

gstreamer-pbutils-sys/build.rs

@@ -43,6 +43,7 @@ fn find() -> Result<(), Error> {
 
     let mut config = Config::new();
     config.atleast_version(version);
+    config.print_system_libs(false);
     if hardcode_shared_libs {
         config.cargo_metadata(false);
     }

gstreamer-player-sys/build.rs

@@ -33,6 +33,7 @@ fn find() -> Result<(), Error> {
 
     let mut config = Config::new();
     config.atleast_version(version);
+    config.print_system_libs(false);
     if hardcode_shared_libs {
         config.cargo_metadata(false);
     }

gstreamer-rtsp-server-sys/build.rs

@@ -45,6 +45,7 @@ fn find() -> Result<(), Error> {
 
     let mut config = Config::new();
     config.atleast_version(version);
+    config.print_system_libs(false);
     if hardcode_shared_libs {
         config.cargo_metadata(false);
     }

gstreamer-rtsp-sys/build.rs

@@ -47,6 +47,7 @@ fn find() -> Result<(), Error> {
 
     let mut config = Config::new();
     config.atleast_version(version);
+    config.print_system_libs(false);
     if hardcode_shared_libs {
         config.cargo_metadata(false);
     }

gstreamer-sdp-sys/build.rs

@@ -45,6 +45,7 @@ fn find() -> Result<(), Error> {
 
     let mut config = Config::new();
     config.atleast_version(version);
+    config.print_system_libs(false);
     if hardcode_shared_libs {
         config.cargo_metadata(false);
     }

gstreamer-sys/build.rs

@@ -49,6 +49,7 @@ fn find() -> Result<(), Error> {
 
     let mut config = Config::new();
     config.atleast_version(version);
+    config.print_system_libs(false);
     if hardcode_shared_libs {
         config.cargo_metadata(false);
     }

gstreamer-tag-sys/build.rs

@@ -45,6 +45,7 @@ fn find() -> Result<(), Error> {
 
     let mut config = Config::new();
     config.atleast_version(version);
+    config.print_system_libs(false);
     if hardcode_shared_libs {
         config.cargo_metadata(false);
     }

gstreamer-video-sys/build.rs

@@ -49,6 +49,7 @@ fn find() -> Result<(), Error> {
 
     let mut config = Config::new();
     config.atleast_version(version);
+    config.print_system_libs(false);
     if hardcode_shared_libs {
         config.cargo_metadata(false);
     }