Fixcrashissue (#4518)

* await for conan downloads
* await later

This fixes #4512 - essentially any exceptions thrown before the `await` of the build environment would leave a "task" that was trying to write to the temp dir. the temp dir would then be deleted, and the untar would fail, and as nobody was await-ing its return (as the awaits used to be _after_ the throwing code) then we'd get an uncaught exception.

lib/base-compiler.ts

@@ -1447,9 +1447,9 @@ export class BaseCompiler implements ICompiler {
     }
 
     async buildExecutableInFolder(key, dirPath): Promise<BuildResult> {
-        const buildEnvironment = this.setupBuildEnvironment(key, dirPath, true);
-
         const writeSummary = await this.writeAllFiles(dirPath, key.source, key.files, key.filters);
+        const downloads = await this.setupBuildEnvironment(key, dirPath, true);
+
         const inputFilename = writeSummary.inputFilename;
 
         const outputFilename = this.getExecutableFilename(dirPath, this.outputFilebase, key);
@@ -1472,7 +1472,6 @@ export class BaseCompiler implements ICompiler {
         const execOptions = this.getDefaultExecOptions();
         execOptions.ldPath = this.getSharedLibraryPathsAsLdLibraryPaths(key.libraries);
 
-        const downloads = await buildEnvironment;
         const result = await this.buildExecutable(key.compiler.exe, compilerArguments, inputFilename, execOptions);
 
         return {
@@ -1714,8 +1713,6 @@ export class BaseCompiler implements ICompiler {
     }
 
     async doCompilation(inputFilename, dirPath, key, options, filters, backendOptions, libraries, tools) {
-        const buildEnvironment = this.setupBuildEnvironment(key, dirPath, filters.binary);
-
         const inputFilenameSafe = this.filename(inputFilename);
 
         const outputFilename = this.getOutputFilename(dirPath, this.outputFilebase, key);
@@ -1742,7 +1739,7 @@ export class BaseCompiler implements ICompiler {
         const makeGccDump =
             backendOptions.produceGccDump && backendOptions.produceGccDump.opened && this.compiler.supportsGccDump;
 
-        const downloads = await buildEnvironment;
+        const downloads = await this.setupBuildEnvironment(key, dirPath, filters.binary);
         const [
             asmResult,
             astResult,