github: Remove nightly Rust installation

ChangeLog:

	* .github/workflows/ccpp.yml: Install Rust 1.72 instead of nightly.
	* .github/workflows/bootstrap.yml: Likewise.

Author: CohenArthur

.github/workflows/bootstrap.yml

@@ -29,7 +29,7 @@ jobs:
                   gcc-multilib \
                   g++-multilib \
                   dejagnu
-          curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y --default-toolchain=nightly;
+          curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y --default-toolchain=1.72.0;
 
     - name: Configure
       run: |

.github/workflows/ccpp.yml

@@ -42,7 +42,7 @@ jobs:
                   g++-multilib \
                   dejagnu;
           # install Rust directly using rustup
-          curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y --default-toolchain=nightly;
+          curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y --default-toolchain=1.72.0;
 
     - name: Configure
       run: |
@@ -123,7 +123,7 @@ jobs:
                   g++-multilib \
                   dejagnu;
           # install Rust directly using rustup
-          curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y --default-toolchain=nightly;
+          curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y --default-toolchain=1.72.0;
 
     - name: Configure
       run: |
@@ -206,7 +206,7 @@ jobs:
                   g++-4.8-multilib \
                   dejagnu;
           # install Rust directly using rustup
-          curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y --default-toolchain=nightly;
+          curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y --default-toolchain=1.72.0;
 
     - name: Configure
       run: |
@@ -265,7 +265,7 @@ jobs:
       run: |
           brew install dejagnu mpfr libmpc gmp;
           # install Rust directly using rustup
-          curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y --default-toolchain=nightly;
+          curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y --default-toolchain=1.72.0;
 
     - name: Configure
       run: |