[analyzer] Try to lift 'REQUIRES: shell' for scan-build tests.

This is the second part of Denys's patch, committed separately
due to being more risky.

Differential Revision: https://reviews.llvm.org/D76768

clang/test/Analysis/scan-build/exclude_directories.test

@@ -1,6 +1,3 @@
-// FIXME: Actually, "perl".
-REQUIRES: shell
-
 RUN: rm -rf %t.output_dir && mkdir %t.output_dir
 RUN: %scan-build -o %t.output_dir %clang -S \
 RUN:     %S/Inputs/multidirectory_project/directory1/file1.c \

clang/test/Analysis/scan-build/help.test

@@ -1,6 +1,3 @@
-// FIXME: Actually, "perl".
-REQUIRES: shell
-
 RUN: %scan-build -h | FileCheck %s
 RUN: %scan-build --help | FileCheck %s
 

clang/test/Analysis/scan-build/html_output.test

@@ -1,6 +1,3 @@
-// FIXME: Actually, "perl".
-REQUIRES: shell
-
 RUN: rm -rf %t.output_dir && mkdir %t.output_dir
 RUN: %scan-build -o %t.output_dir %clang -S %S/Inputs/single_null_dereference.c \
 RUN:     | FileCheck %s -check-prefix CHECK-STDOUT

clang/test/Analysis/scan-build/plist_html_output.test

@@ -1,6 +1,3 @@
-// FIXME: Actually, "perl".
-REQUIRES: shell
-
 RUN: rm -rf %t.output_dir && mkdir %t.output_dir
 RUN: %scan-build -plist-html -o %t.output_dir %clang -S %S/Inputs/single_null_dereference.c \
 RUN:     | FileCheck %s -check-prefix CHECK-STDOUT

clang/test/Analysis/scan-build/plist_output.test

@@ -1,6 +1,3 @@
-// FIXME: Actually, "perl".
-REQUIRES: shell
-
 RUN: rm -rf %t.output_dir && mkdir %t.output_dir
 RUN: %scan-build -plist -o %t.output_dir %clang -S %S/Inputs/single_null_dereference.c \
 RUN:     | FileCheck %s -check-prefix CHECK-STDOUT