lea 0.87.0 compiler dependency update (#829)

* Update lea-0.87.0.toml

The choice of GNAT version is improved.
The previous state forced to a version of GNAT which is supported by Alire.
This assumed a GNAT already installed outside of Alire.
Absent that, the build fails.

* Update lea-0.87.0.toml

Indicate that there is an executable built.
This removes the message:
"Crate lea does not explicitly declares to build any executable
However, the following default executables have been autodetected"

* Update lea-0.87.0.toml

Alire seems not to expect a file name extension for the executable:
"Crate lea builds these executables:
   lea.exe.exe (not found)"

index/le/lea/lea-0.87.0.toml

@@ -10,6 +10,7 @@ licenses = "MIT"
 tags = ["lea", "editor"]
 
 project-files = ["lea_project_tree.gpr"]
+executables = ["lea"]
 
 [available.'case(os)']
 windows = true
@@ -30,7 +31,7 @@ gwindows = "^1.4.0"
 [[depends-on]]
 zipada = "^58.0.0"
 [[depends-on]]
-gnat = "<10.3.1"
+gnat = "/=10.3.2"
 [[depends-on]]
 hac = "~0.22.0"