build: use magic target/release/ path prefix

Both cargo-deb and cargo-generate-rpm treat the "target/release/" path
prefix specially, replacing this prefix based on the build target and
profile specified on the command line.

N.B. cargo-generate-rpm gained support for --profile in
cat-in-136/cargo-generate-rpm@9dd158bbb, which is
not yet released, but is present on the profile-option branch of
https://github.com/jpgrayson/cargo-generate-rpm which is used for CI.

Author: jpgrayson

Cargo.toml

@@ -66,7 +66,7 @@ depends = "git"
 recommends = "git-email"
 extended-description = ""
 assets = [
-  ["target/for-pkg/stg", "usr/bin/", "755"],
+  ["target/release/stg", "usr/bin/", "755"],
   ["README.md", "usr/share/doc/stgit/", "644"],
   ["COPYING", "usr/share/doc/stgit/copyright", "644"],
   ["Documentation/*.1", "usr/share/man/man1/", "644"],
@@ -79,7 +79,7 @@ assets = [
 
 [package.metadata.generate-rpm]
 assets = [
-  { source = "target/for-pkg/stg", dest = "/usr/bin/", mode = "755" },
+  { source = "target/release/stg", dest = "/usr/bin/", mode = "755" },
   { source = "README.md", dest = "/usr/share/doc/stgit/", mode = "644" },
   { source = "COPYING", dest = "/usr/share/licenses/stgit/", mode = "644" },
   { source = "Documentation/*.1", dest = "/usr/share/man/man1/", mode = "644", doc = true },