meson(cargo): Visual C produces gitcore.lib, not libgitcore.a

On Windows, when Visual C compiler is used to compile, the resulting
library that is created is called gitcore.lib instead of libgitcore.a
library archive.

Johannes sent a fix in <dc753c0e-eb93-948c-55f7-bb0e91772c83@gmx.de>
that was based on an older code base, which I attempted to forward
port it to apply to today's codebase.

Based-on-the-patch-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: gitster

src/cargo-meson.sh

@@ -7,9 +7,10 @@ fi
 
 SOURCE_DIR="$1"
 BUILD_DIR="$2"
+LIBNAME="$3"
 BUILD_TYPE=debug
 
-shift 2
+shift 3
 
 for arg
 do
@@ -26,14 +27,7 @@ then
 	exit $RET
 fi
 
-case "$(cargo -vV | sed -s 's/^host: \(.*\)$/\1/')" in
-	*-windows-*)
-		LIBNAME=gitcore.lib;;
-	*)
-		LIBNAME=libgitcore.a;;
-esac
-
-if ! cmp "$BUILD_DIR/$BUILD_TYPE/$LIBNAME" "$BUILD_DIR/libgitcore.a" >/dev/null 2>&1
+if ! cmp "$BUILD_DIR/$BUILD_TYPE/$LIBNAME" "$BUILD_DIR/$LIBNAME" >/dev/null 2>&1
 then
-	cp "$BUILD_DIR/$BUILD_TYPE/$LIBNAME" "$BUILD_DIR/libgitcore.a"
+	cp "$BUILD_DIR/$BUILD_TYPE/$LIBNAME" "$BUILD_DIR/$LIBNAME"
 fi

src/meson.build

@@ -3,6 +3,14 @@ libgit_rs_sources = [
   'varint.rs',
 ]
 
+# The exact file name depends on the compiler
+if meson.get_compiler('c').get_id() == 'msvc'
+  libname = 'gitcore.lib'
+else
+  libname = 'libgitcore.a'
+endif
+
+
 # Unfortunately we must use a wrapper command to move the output file into the
 # current build directory. This can fixed once `cargo build --artifact-dir`
 # stabilizes. See https://github.com/rust-lang/cargo/issues/6790 for that
@@ -12,6 +20,7 @@ cargo_command = [
   meson.current_source_dir() / 'cargo-meson.sh',
   meson.project_source_root(),
   meson.current_build_dir(),
+  libname,
 ]
 if get_option('buildtype') == 'release'
   cargo_command += '--release'
@@ -21,7 +30,7 @@ libgit_rs = custom_target('git_rs',
   input: libgit_rs_sources + [
     meson.project_source_root() / 'Cargo.toml',
   ],
-  output: 'libgitcore.a',
+  output: libname,
   command: cargo_command,
 )
 libgit_dependencies += declare_dependency(link_with: libgit_rs)