feat: lake: CMake build types (#10578)

This PR adds support for the CMake spelling of a build type (i.e.,
capitalized) to Lake's `buildType` configuration option.

src/lake/Lake/Config/LeanConfig.lean

@@ -118,7 +118,7 @@ public def leancArgs : BuildType → Array String
 | release => #["-O3", "-DNDEBUG"]
 
 public def ofString? (s : String) : Option BuildType :=
-  match s with
+  match s.decapitalize with
   | "debug" => some .debug
   | "relWithDebInfo" => some .relWithDebInfo
   | "minSizeRel" => some .minSizeRel

src/lake/tests/translateConfig/source.toml

@@ -16,7 +16,7 @@ releaseRepo = ""
 buildArchive = ""
 preferReleaseBuild = false
 packagesDir = ".lake/packages"
-buildType = "release"
+buildType = "Release"
 leanOptions = []
 moreServerOptions = []
 moreLeanArgs = []