Add $CARGO_INSTALL_OPTS to manpage. Fix Rust 1.35.0 builds

h/t @elichai for a =ver dep instead of a patch

Ref: #119

Cargo.toml

@@ -30,6 +30,12 @@ exclude = ["*.enc"]
 
 # Note: don't bump dependencies unless necessary to keep building on old rustc versions
 [dependencies]
+# https://travis-ci.org/nabijaczleweli/cargo-update/jobs/619241497#L222 broke 1.35.0 with smallvec 1.0.0,
+# required by unicode-normalization 0.1.11. Previous working build is
+# https://travis-ci.org/nabijaczleweli/cargo-update/jobs/611381166#L271 with unicode-normalization 0.1.9
+# h/t to @elichai in https://github.com/nabijaczleweli/cargo-update/issues/119#issuecomment-560116619
+# for suggesting using a `=` dep instead of a patch
+unicode-normalization="=0.1.9"
 serde_derive = "1.0"
 lazy_static = "1.4"
 array_tool = "1.0"

man/cargo-install-update.md

@@ -16,6 +16,11 @@ Updates packages from the main repository and git repositories.
 
 See cargo-install-update-config(1) for further configuring updates.
 
+The `CARGO_INSTALL_OPTS` environment variable can be set,
+containing options to forward to the end of `cargo install` invocations'
+argument lists.
+Note, that cargo-install-update-config(1) is preferred in the general case.
+
 Exit values and possible errors:
 
     -1 - cargo subprocess was terminated by a signal (Linux-only)