[librsvg] Have "make V=1" pass --verbose to "cargo build"

[Federico Mena Quintero <federico src gnome org>]

commit 0a4afff7549525060bdff7ba5e1604c9ee10861f
Author: Federico Mena Quintero <federico gnome org>
Date:   Fri Sep 1 16:45:33 2017 -0500

    Have "make V=1" pass --verbose to "cargo build"

 Makefile.am |    7 ++++++-
 1 files changed, 6 insertions(+), 1 deletions(-)
---
diff --git a/Makefile.am b/Makefile.am
index 048bdca..5e71b38 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -109,6 +109,11 @@ else
 CARGO_RELEASE_ARGS=--release
 endif
 
+CARGO_VERBOSE = $(cargo_verbose_$(V))
+cargo_verbose_ = $(cargo_verbose_$(AM_DEFAULT_VERBOSITY))
+cargo_verbose_0 =
+cargo_verbose_1 = --verbose
+
 RUST_LIB=@abs_top_builddir@/rust/target/@RUST_TARGET_SUBDIR@/librsvg_internals.a
 
 check-local:
@@ -127,7 +132,7 @@ dist-hook:
 
 @abs_top_builddir@/rust/target/@RUST_TARGET_SUBDIR@/librsvg_internals.a: $(RUST_SOURCES)
        cd $(top_srcdir)/rust && \
-       CARGO_TARGET_DIR=@abs_top_builddir@/rust/target cargo build $(CARGO_RELEASE_ARGS)
+       CARGO_TARGET_DIR=@abs_top_builddir@/rust/target cargo build $(CARGO_VERBOSE) $(CARGO_RELEASE_ARGS)
 
 librsvg_@RSVG_API_MAJOR_VERSION@_la_CPPFLAGS = \
        -I$(top_srcdir)                         \