Add NO_BUILD and NO_BUILD_PACKAGE environment variables (#11968)

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## Summary

<!-- What's the purpose of the change? What does it do, and why? -->
Similar to https://github.com/astral-sh/uv/pull/11399

This adds `UV_NO_BUILD` and `UV_NO_BUILD_PACKAGE` environment variables
for non-pip commands.

## Test Plan

<!-- How was it tested? -->
Tested manually and with snapshot tests.


Fixes #11963

Signed-off-by: Alex Lowe <alex@lowe.dev>

docs/configuration/environment.md

@@ -195,11 +195,21 @@ extract package metadata, if available.
 Equivalent to the `--no-binary-package` command line argument. If set, uv will
 not use pre-built wheels for the given space-delimited list of packages.
 
+### `UV_NO_BUILD`
+
+Equivalent to the `--no-build` command-line argument. If set, uv will not build
+source distributions.
+
 ### `UV_NO_BUILD_ISOLATION`
 
 Equivalent to the `--no-build-isolation` command-line argument. If set, uv will
 skip isolation when building source distributions.
 
+### `UV_NO_BUILD_PACKAGE`
+
+Equivalent to the `--no-build-package` command line argument. If set, uv will
+not build source distributions for the given space-delimited list of packages.
+
 ### `UV_NO_CACHE`
 
 Equivalent to the `--no-cache` command-line argument. If set, uv will not use the